diff --git a/coverage/htmlfiles/pyfile.html b/coverage/htmlfiles/pyfile.html
index eb0f99c81..ec0f416ff 100644
--- a/coverage/htmlfiles/pyfile.html
+++ b/coverage/htmlfiles/pyfile.html
@@ -33,12 +33,12 @@ <h1>Coverage for <b>{{relative_filename|escape}}</b> :
 
         <h2 class="stats">
             {{nums.n_statements}} statements &nbsp;
-            <span class="{{category.run}} shortkey_r button_toggle_run">{{nums.n_executed}} run</span>
-            <span class="{{category.mis}} shortkey_m button_toggle_mis">{{nums.n_missing}} missing</span>
-            <span class="{{category.exc}} shortkey_x button_toggle_exc">{{nums.n_excluded}} excluded</span>
+            <button type="button" class="{{category.run}} shortkey_r button_toggle_run" title="Toggle lines run">{{nums.n_executed}} run</button>
+            <button type="button" class="{{category.mis}} shortkey_m button_toggle_mis" title="Toggle lines missing">{{nums.n_missing}} missing</button>
+            <button type="button" class="{{category.exc}} shortkey_x button_toggle_exc" title="Toggle lines excluded">{{nums.n_excluded}} excluded</button>
 
             {% if has_arcs %}
-                <span class="{{category.par}} shortkey_p button_toggle_par">{{nums.n_partial_branches}} partial</span>
+            <button type="button" class="{{category.par}} shortkey_p button_toggle_par" title="Toggle lines partially run">{{nums.n_partial_branches}} partial</button>
             {% endif %}
         </h2>
     </div>
diff --git a/coverage/htmlfiles/style.css b/coverage/htmlfiles/style.css
index e8ff57657..ab9dbcb9d 100644
--- a/coverage/htmlfiles/style.css
+++ b/coverage/htmlfiles/style.css
@@ -4,11 +4,17 @@
 /* Don't edit this .css file. Edit the .scss file instead! */
 html, body, h1, h2, h3, p, table, td, th { margin: 0; padding: 0; border: 0; font-weight: inherit; font-style: inherit; font-size: 100%; font-family: inherit; vertical-align: baseline; }
 
-body { font-family: georgia, serif; font-size: 1em; }
+body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; font-size: 1em; background: #fff; color: #000; }
+
+@media (prefers-color-scheme: dark) { body { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { body { color: #eee; } }
 
 html > body { font-size: 16px; }
 
-p { font-size: .75em; line-height: 1.33333333em; }
+a:active, a:focus { outline: 2px dashed #007acc; }
+
+p { font-size: .875em; line-height: 1.4em; }
 
 table { border-collapse: collapse; }
 
@@ -19,15 +25,22 @@ table tr.hidden { display: none !important; }
 p#no_rows { display: none; font-size: 1.2em; }
 
 a.nav { text-decoration: none; color: inherit; }
+
 a.nav:hover { text-decoration: underline; color: inherit; }
 
 #header { background: #f8f8f8; width: 100%; border-bottom: 1px solid #eee; }
 
+@media (prefers-color-scheme: dark) { #header { background: black; } }
+
+@media (prefers-color-scheme: dark) { #header { border-color: #333; } }
+
 .indexfile #footer { margin: 1em 3em; }
 
 .pyfile #footer { margin: 1em 1em; }
 
-#footer .content { padding: 0; font-size: 85%; font-family: verdana, sans-serif; color: #666666; font-style: italic; }
+#footer .content { padding: 0; color: #666; font-style: italic; }
+
+@media (prefers-color-scheme: dark) { #footer .content { color: #aaa; } }
 
 #index { margin: 1em 0 0 3em; }
 
@@ -35,90 +48,236 @@ a.nav:hover { text-decoration: underline; color: inherit; }
 
 h1 { font-size: 1.25em; display: inline-block; }
 
-#filter_container { display: inline-block; float: right; margin: 0 2em 0 0; }
-#filter_container input { width: 10em; }
+#filter_container { float: right; margin: 0 2em 0 0; }
+
+#filter_container input { width: 10em; padding: 0.2em 0.5em; border: 2px solid #ccc; background: #fff; color: #000; }
+
+@media (prefers-color-scheme: dark) { #filter_container input { border-color: #444; } }
+
+@media (prefers-color-scheme: dark) { #filter_container input { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { #filter_container input { color: #eee; } }
+
+#filter_container input:focus { border-color: #007acc; }
 
 h2.stats { margin-top: .5em; font-size: 1em; }
 
-.stats span { border: 1px solid; border-radius: .1em; padding: .1em .5em; margin: 0 .1em; cursor: pointer; border-color: #ccc #999 #999 #ccc; }
-.stats span.run { background: #eeffee; }
-.stats span.run.show_run { border-color: #999 #ccc #ccc #999; background: #ddffdd; }
-.stats span.mis { background: #ffeeee; }
-.stats span.mis.show_mis { border-color: #999 #ccc #ccc #999; background: #ffdddd; }
-.stats span.exc { background: #f7f7f7; }
-.stats span.exc.show_exc { border-color: #999 #ccc #ccc #999; background: #eeeeee; }
-.stats span.par { background: #ffffd5; }
-.stats span.par.show_par { border-color: #999 #ccc #ccc #999; background: #ffffaa; }
+.stats button { font-family: inherit; font-size: inherit; border: 2px solid; border-radius: .1em; color: inherit; padding: .1em .5em; margin: 0 .1em; cursor: pointer; border-color: #ccc; }
+
+@media (prefers-color-scheme: dark) { .stats button { border-color: #444; } }
+
+.stats button:active, .stats button:focus { outline: 2px dashed #007acc; }
+
+.stats button:active, .stats button:focus { outline: 2px dashed #007acc; }
+
+.stats button.run { background: #eeffee; }
+
+@media (prefers-color-scheme: dark) { .stats button.run { background: #373d29; } }
+
+.stats button.run.show_run { background: #dfd; border-color: #00dd00; }
+
+@media (prefers-color-scheme: dark) { .stats button.run.show_run { background: #373d29; } }
+
+.stats button.mis { background: #ffeeee; }
+
+@media (prefers-color-scheme: dark) { .stats button.mis { background: #4b1818; } }
+
+.stats button.mis.show_mis { background: #fdd; border-color: #ff0000; }
+
+@media (prefers-color-scheme: dark) { .stats button.mis.show_mis { background: #4b1818; } }
+
+.stats button.exc { background: #f7f7f7; }
+
+@media (prefers-color-scheme: dark) { .stats button.exc { background: #333; } }
+
+.stats button.exc.show_exc { background: #eee; border-color: #808080; }
+
+@media (prefers-color-scheme: dark) { .stats button.exc.show_exc { background: #333; } }
+
+.stats button.par { background: #ffffd5; }
 
-#source p .annotate.long, .help_panel { display: none; position: absolute; z-index: 999; background: #ffffcc; border: 1px solid #888; border-radius: .2em; box-shadow: #cccccc .2em .2em .2em; color: #333; padding: .25em .5em; }
+@media (prefers-color-scheme: dark) { .stats button.par { background: #650; } }
+
+.stats button.par.show_par { background: #ffa; border-color: #dddd00; }
+
+@media (prefers-color-scheme: dark) { .stats button.par.show_par { background: #650; } }
+
+.help_panel, #source p .annotate.long { display: none; position: absolute; z-index: 999; background: #ffffcc; border: 1px solid #888; border-radius: .2em; color: #333; padding: .25em .5em; }
 
 #source p .annotate.long { white-space: normal; float: right; top: 1.75em; right: 1em; height: auto; }
 
 #keyboard_icon { float: right; margin: 5px; cursor: pointer; }
 
 .help_panel { padding: .5em; border: 1px solid #883; }
+
 .help_panel .legend { font-style: italic; margin-bottom: 1em; }
-.indexfile .help_panel { width: 20em; height: 4em; }
-.pyfile .help_panel { width: 16em; height: 8em; }
+
+.indexfile .help_panel { width: 20em; min-height: 4em; }
+
+.pyfile .help_panel { width: 16em; min-height: 8em; }
 
 #panel_icon { float: right; cursor: pointer; }
 
 .keyhelp { margin: .75em; }
-.keyhelp .key { border: 1px solid black; border-color: #888 #333 #333 #888; padding: .1em .35em; font-family: monospace; font-weight: bold; background: #eee; }
 
-#source { padding: 1em 0 1em 3rem; font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace; }
+.keyhelp .key { border: 1px solid black; border-color: #888 #333 #333 #888; padding: .1em .35em; font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; font-weight: bold; background: #eee; }
+
+#source { padding: 1em 0 1em 3rem; font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; }
+
 #source p { position: relative; white-space: pre; }
+
 #source p * { box-sizing: border-box; }
-#source p .n { float: left; text-align: right; width: 3rem; box-sizing: border-box; margin-left: -3rem; padding-right: 1em; color: #999999; font-family: verdana, sans-serif; }
-#source p .n a { text-decoration: none; color: #999999; font-size: .8333em; line-height: 1em; }
-#source p .n a:hover { text-decoration: underline; color: #999999; }
+
+#source p .n { float: left; text-align: right; width: 3rem; box-sizing: border-box; margin-left: -3rem; padding-right: 1em; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n { color: #777; } }
+
+#source p .n a { text-decoration: none; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n a { color: #777; } }
+
+#source p .n a:hover { text-decoration: underline; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n a:hover { color: #777; } }
+
 #source p.highlight .n { background: #ffdd00; }
-#source p .t { display: inline-block; width: 100%; box-sizing: border-box; margin-left: -.5em; padding-left: 0.3em; border-left: 0.2em solid white; }
+
+#source p .t { display: inline-block; width: 100%; box-sizing: border-box; margin-left: -.5em; padding-left: 0.3em; border-left: 0.2em solid #fff; }
+
+@media (prefers-color-scheme: dark) { #source p .t { border-color: #1e1e1e; } }
+
 #source p .t:hover { background: #f2f2f2; }
+
+@media (prefers-color-scheme: dark) { #source p .t:hover { background: #282828; } }
+
 #source p .t:hover ~ .r .annotate.long { display: block; }
-#source p .t .com { color: green; font-style: italic; line-height: 1px; }
+
+#source p .t .com { color: #008000; font-style: italic; line-height: 1px; }
+
+@media (prefers-color-scheme: dark) { #source p .t .com { color: #6A9955; } }
+
 #source p .t .key { font-weight: bold; line-height: 1px; }
-#source p .t .str { color: #000080; }
+
+#source p .t .str { color: #0451A5; }
+
+@media (prefers-color-scheme: dark) { #source p .t .str { color: #9CDCFE; } }
+
 #source p.mis .t { border-left: 0.2em solid #ff0000; }
-#source p.mis.show_mis .t { background: #ffdddd; }
+
+#source p.mis.show_mis .t { background: #fdd; }
+
+@media (prefers-color-scheme: dark) { #source p.mis.show_mis .t { background: #4b1818; } }
+
 #source p.mis.show_mis .t:hover { background: #f2d2d2; }
-#source p.run .t { border-left: 0.2em solid #00ff00; }
-#source p.run.show_run .t { background: #ddffdd; }
+
+@media (prefers-color-scheme: dark) { #source p.mis.show_mis .t:hover { background: #532323; } }
+
+#source p.run .t { border-left: 0.2em solid #00dd00; }
+
+#source p.run.show_run .t { background: #dfd; }
+
+@media (prefers-color-scheme: dark) { #source p.run.show_run .t { background: #373d29; } }
+
 #source p.run.show_run .t:hover { background: #d2f2d2; }
+
+@media (prefers-color-scheme: dark) { #source p.run.show_run .t:hover { background: #404633; } }
+
 #source p.exc .t { border-left: 0.2em solid #808080; }
-#source p.exc.show_exc .t { background: #eeeeee; }
+
+#source p.exc.show_exc .t { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #source p.exc.show_exc .t { background: #333; } }
+
 #source p.exc.show_exc .t:hover { background: #e2e2e2; }
-#source p.par .t { border-left: 0.2em solid #eeee99; }
-#source p.par.show_par .t { background: #ffffaa; }
+
+@media (prefers-color-scheme: dark) { #source p.exc.show_exc .t:hover { background: #3c3c3c; } }
+
+#source p.par .t { border-left: 0.2em solid #dddd00; }
+
+#source p.par.show_par .t { background: #ffa; }
+
+@media (prefers-color-scheme: dark) { #source p.par.show_par .t { background: #650; } }
+
 #source p.par.show_par .t:hover { background: #f2f2a2; }
-#source p .r { position: absolute; top: 0; right: 2.5em; font-family: verdana, sans-serif; }
-#source p .annotate { font-family: georgia; color: #666; padding-right: .5em; }
+
+@media (prefers-color-scheme: dark) { #source p.par.show_par .t:hover { background: #6d5d0c; } }
+
+#source p .r { position: absolute; top: 0; right: 2.5em; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; }
+
+#source p .annotate { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; color: #666; padding-right: .5em; }
+
+@media (prefers-color-scheme: dark) { #source p .annotate { color: #ddd; } }
+
 #source p .annotate.short:hover ~ .long { display: block; }
+
 #source p .annotate.long { width: 30em; right: 2.5em; }
+
 #source p input { display: none; }
+
 #source p input ~ .r label.ctx { cursor: pointer; border-radius: .25em; }
+
 #source p input ~ .r label.ctx::before { content: "▶ "; }
+
 #source p input ~ .r label.ctx:hover { background: #d5f7ff; color: #666; }
+
 #source p input:checked ~ .r label.ctx { background: #aaeeff; color: #666; border-radius: .75em .75em 0 0; padding: 0 .5em; margin: -.25em 0; }
+
 #source p input:checked ~ .r label.ctx::before { content: "▼ "; }
+
 #source p input:checked ~ .ctxs { padding: .25em .5em; overflow-y: scroll; max-height: 10.5em; }
+
 #source p label.ctx { color: #999; display: inline-block; padding: 0 .5em; font-size: .8333em; }
-#source p .ctxs { display: block; max-height: 0; overflow-y: hidden; transition: all .2s; padding: 0 .5em; font-family: verdana, sans-serif; white-space: nowrap; background: #aaeeff; border-radius: .25em; margin-right: 1.75em; }
+
+@media (prefers-color-scheme: dark) { #source p label.ctx { color: #777; } }
+
+#source p .ctxs { display: block; max-height: 0; overflow-y: hidden; transition: all .2s; padding: 0 .5em; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; white-space: nowrap; background: #aaeeff; border-radius: .25em; margin-right: 1.75em; }
+
 #source p .ctxs span { display: block; text-align: right; }
 
+#index { font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; font-size: 0.875em; }
+
 #index td, #index th { text-align: right; width: 5em; padding: .25em .5em; border-bottom: 1px solid #eee; }
+
+@media (prefers-color-scheme: dark) { #index td, #index th { border-color: #333; } }
+
 #index td.left, #index th.left { padding-left: 0; }
+
 #index td.right, #index th.right { padding-right: 0; }
+
 #index td.name, #index th.name { text-align: left; width: auto; }
-#index th { font-style: italic; color: #333; border-bottom: 1px solid #ccc; cursor: pointer; }
-#index th:hover { background: #eee; border-bottom: 1px solid #999; }
-#index th.headerSortDown, #index th.headerSortUp { border-bottom: 1px solid #000; white-space: nowrap; background: #eee; }
+
+#index th { font-style: italic; color: #333; cursor: pointer; }
+
+@media (prefers-color-scheme: dark) { #index th { color: #ddd; } }
+
+#index th:hover { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index th:hover { background: #333; } }
+
+#index th.headerSortDown, #index th.headerSortUp { white-space: nowrap; background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index th.headerSortDown, #index th.headerSortUp { background: #333; } }
+
 #index th.headerSortDown:after { content: " ↓"; }
+
 #index th.headerSortUp:after { content: " ↑"; }
-#index td.name a { text-decoration: none; color: #000; }
+
+#index td.name a { text-decoration: none; color: inherit; }
+
 #index tr.total td, #index tr.total_dynamic td { font-weight: bold; border-top: 1px solid #ccc; border-bottom: none; }
-#index tr.file:hover { background: #eeeeee; }
-#index tr.file:hover td.name { text-decoration: underline; color: #000; }
 
-#scroll_marker { position: fixed; right: 0; top: 0; width: 16px; height: 100%; background: white; border-left: 1px solid #eee; will-change: transform; }
-#scroll_marker .marker { background: #ddd; position: absolute; min-height: 3px; width: 100%; }
+#index tr.file:hover { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index tr.file:hover { background: #333; } }
+
+#index tr.file:hover td.name { text-decoration: underline; color: inherit; }
+
+#scroll_marker { position: fixed; right: 0; top: 0; width: 16px; height: 100%; background: #fff; border-left: 1px solid #eee; will-change: transform; }
+
+@media (prefers-color-scheme: dark) { #scroll_marker { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { #scroll_marker { border-color: #333; } }
+
+#scroll_marker .marker { background: #ccc; position: absolute; min-height: 3px; width: 100%; }
+
+@media (prefers-color-scheme: dark) { #scroll_marker .marker { background: #444; } }
diff --git a/coverage/htmlfiles/style.scss b/coverage/htmlfiles/style.scss
index 901cccc4e..b6efec1b2 100644
--- a/coverage/htmlfiles/style.scss
+++ b/coverage/htmlfiles/style.scss
@@ -8,6 +8,9 @@
 
 // When working on the file, this command is useful:
 //      sass --watch --style=compact --sourcemap=none --no-cache coverage/htmlfiles/style.scss:htmlcov/style.css
+//
+// OR you can process sass purely in python with `pip install pysass`, then:
+//      pysassc --style=compact coverage/htmlfiles/style.scss coverage/htmlfiles/style.css
 
 // Ignore this comment, it's for the CSS output file:
 /* Don't edit this .css file. Edit the .scss file instead! */
@@ -15,6 +18,82 @@
 // Dimensions
 $left-gutter: 3rem;
 
+
+//
+// Declare colors and variables
+//
+
+$font-normal:             -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif;
+$font-code:               SFMono-Regular, Menlo, Monaco, Consolas, monospace;
+
+$off-button-lighten:      50%;
+$hover-dark-amt:          95%;
+
+$focus-color:             #007acc;
+
+$mis-color:               #ff0000;
+$run-color:               #00dd00;
+$exc-color:               #808080;
+$par-color:               #dddd00;
+
+$light-bg:                #fff;
+$light-fg:                #000;
+$light-gray1:             #f8f8f8;
+$light-gray2:             #eee;
+$light-gray3:             #ccc;
+$light-gray4:             #999;
+$light-gray5:             #666;
+$light-gray6:             #333;
+$light-pln-bg:            $light-bg;
+$light-mis-bg:            #fdd;
+$light-run-bg:            #dfd;
+$light-exc-bg:            $light-gray2;
+$light-par-bg:            #ffa;
+$light-token-com:         #008000;
+$light-token-str:         #0451A5;
+
+$dark-bg:                 #1e1e1e;
+$dark-fg:                 #eee;
+$dark-gray1:              #222;
+$dark-gray2:              #333;
+$dark-gray3:              #444;
+$dark-gray4:              #777;
+$dark-gray5:              #aaa;
+$dark-gray6:              #ddd;
+$dark-pln-bg:             $dark-bg;
+$dark-mis-bg:             #4b1818;
+$dark-run-bg:             #373d29;
+$dark-exc-bg:             $dark-gray2;
+$dark-par-bg:             #650;
+$dark-token-com:          #6A9955;
+$dark-token-str:          #9CDCFE;
+
+//
+// Mixins and utilities
+//
+@mixin background-dark($color) {
+    @media (prefers-color-scheme: dark) {
+        background: $color;
+    }
+}
+@mixin color-dark($color) {
+    @media (prefers-color-scheme: dark) {
+        color: $color;
+    }
+}
+@mixin border-color-dark($color) {
+    @media (prefers-color-scheme: dark) {
+        border-color: $color;
+    }
+}
+
+// Add visual outline to navigable elements on focus improve accessibility.
+@mixin focus-border {
+    &:active, &:focus {
+        outline: 2px dashed $focus-color;
+    }
+}
+
 // Page-wide styles
 html, body, h1, h2, h3, p, table, td, th {
     margin: 0;
@@ -29,18 +108,25 @@ html, body, h1, h2, h3, p, table, td, th {
 
 // Set baseline grid to 16 pt.
 body {
-    font-family: georgia, serif;
+    font-family: $font-normal;
     font-size: 1em;
+    background: $light-bg;
+    color: $light-fg;
+    @include background-dark($dark-bg);
+    @include color-dark($dark-fg);
 }
 
 html>body {
     font-size: 16px;
 }
 
-// Set base font size to 12/16
+a {
+    @include focus-border;
+}
+
 p {
-    font-size: .75em;           // 12/16
-    line-height: 1.33333333em;  // 16/12
+    font-size: .875em;
+    line-height: 1.4em;
 }
 
 table {
@@ -70,9 +156,11 @@ a.nav {
 
 // Page structure
 #header {
-    background: #f8f8f8;
+    background: $light-gray1;
+    @include background-dark(black);
     width: 100%;
-    border-bottom: 1px solid #eee;
+    border-bottom: 1px solid $light-gray2;
+    @include border-color-dark($dark-gray2);
 }
 
 .indexfile #footer {
@@ -85,9 +173,8 @@ a.nav {
 
 #footer .content {
     padding: 0;
-    font-size: 85%;
-    font-family: verdana, sans-serif;
-    color: #666666;
+    color: $light-gray5;
+    @include color-dark($dark-gray5);
     font-style: italic;
 }
 
@@ -106,61 +193,77 @@ h1 {
 }
 
 #filter_container {
-    display: inline-block;
     float: right;
     margin: 0 2em 0 0;
 
     input {
         width: 10em;
+        padding: 0.2em 0.5em;
+        border: 2px solid $light-gray3;
+        background: $light-bg;
+        color: $light-fg;
+        @include border-color-dark($dark-gray3);
+        @include background-dark($dark-bg);
+        @include color-dark($dark-fg);
+        &:focus {
+            border-color: $focus-color;
+        }
     }
 }
 
-$pln-color: #ffffff;
-$mis-color: #ffdddd;
-$run-color: #ddffdd;
-$exc-color: #eeeeee;
-$par-color: #ffffaa;
-
-$off-button-lighten: 50%;
-
 h2.stats {
     margin-top: .5em;
     font-size: 1em;
 }
-.stats span {
-    border: 1px solid;
+.stats button {
+    font-family: inherit;
+    font-size: inherit;
+    border: 2px solid;
     border-radius: .1em;
+    color: inherit;
     padding: .1em .5em;
     margin: 0 .1em;
     cursor: pointer;
-    border-color: #ccc #999 #999 #ccc;
+    border-color: $light-gray3;
+    @include border-color-dark($dark-gray3);
+    @include focus-border;
+
+    @include focus-border;
 
     &.run {
-        background: mix($run-color, #fff, $off-button-lighten);
+        background: mix($light-run-bg, $light-bg, $off-button-lighten);
+        @include background-dark($dark-run-bg);
         &.show_run {
-            border-color: #999 #ccc #ccc #999;
-            background: $run-color;
+            background: $light-run-bg;
+            @include background-dark($dark-run-bg);
+            border-color: $run-color;
         }
     }
     &.mis {
-        background: mix($mis-color, #fff, $off-button-lighten);
+        background: mix($light-mis-bg, $light-bg, $off-button-lighten);
+        @include background-dark($dark-mis-bg);
         &.show_mis {
-            border-color: #999 #ccc #ccc #999;
-            background: $mis-color;
+            background: $light-mis-bg;
+            @include background-dark($dark-mis-bg);
+            border-color: $mis-color;
         }
     }
     &.exc {
-        background: mix($exc-color, #fff, $off-button-lighten);
+        background: mix($light-exc-bg, $light-bg, $off-button-lighten);
+        @include background-dark($dark-exc-bg);
         &.show_exc {
-            border-color: #999 #ccc #ccc #999;
-            background: $exc-color;
+            background: $light-exc-bg;
+            @include background-dark($dark-exc-bg);
+            border-color: $exc-color;
         }
     }
     &.par {
-        background: mix($par-color, #fff, $off-button-lighten);
+        background: mix($light-par-bg, $light-bg, $off-button-lighten);
+        @include background-dark($dark-par-bg);
         &.show_par {
-            border-color: #999 #ccc #ccc #999;
-            background: $par-color;
+            background: $light-par-bg;
+            @include background-dark($dark-par-bg);
+            border-color: $par-color;
         }
     }
 }
@@ -173,7 +276,6 @@ h2.stats {
     background: #ffffcc;
     border: 1px solid #888;
     border-radius: .2em;
-    box-shadow: #cccccc .2em .2em .2em;
     color: #333;
     padding: .25em .5em;
 }
@@ -207,12 +309,12 @@ h2.stats {
 
     .indexfile & {
         width: 20em;
-        height: 4em;
+        min-height: 4em;
     }
 
     .pyfile & {
         width: 16em;
-        height: 8em;
+        min-height: 8em;
     }
 }
 
@@ -228,7 +330,7 @@ h2.stats {
         border: 1px solid black;
         border-color: #888 #333 #333 #888;
         padding: .1em .35em;
-        font-family: monospace;
+        font-family: $font-code;
         font-weight: bold;
         background: #eee;
     }
@@ -236,13 +338,6 @@ h2.stats {
 
 // Source file styles
 
-$hover-dark-amt: 95%;
-$pln-hover-color: mix($pln-color, #000, $hover-dark-amt);
-$mis-hover-color: mix($mis-color, #000, $hover-dark-amt);
-$run-hover-color: mix($run-color, #000, $hover-dark-amt);
-$exc-hover-color: mix($exc-color, #000, $hover-dark-amt);
-$par-hover-color: mix($par-color, #000, $hover-dark-amt);
-
 // The slim bar at the left edge of the source lines, colored by coverage.
 $border-indicator-width: .2em;
 
@@ -250,7 +345,7 @@ $context-panel-color: #aaeeff;
 
 #source {
     padding: 1em 0 1em $left-gutter;
-    font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace;
+    font-family: $font-code;
 
     p {
         // position relative makes position:absolute pop-ups appear in the right place.
@@ -268,17 +363,17 @@ $context-panel-color: #aaeeff;
             box-sizing: border-box;
             margin-left: -$left-gutter;
             padding-right: 1em;
-            color: #999999;
-            font-family: verdana, sans-serif;
+            color: $light-gray4;
+            @include color-dark($dark-gray4);
 
             a {
                 text-decoration: none;
-                color: #999999;
-                font-size: .8333em;   // 10/12
-                line-height: 1em;
+                color: $light-gray4;
+                @include color-dark($dark-gray4);
                 &:hover {
                     text-decoration: underline;
-                    color: #999999;
+                    color: $light-gray4;
+                    @include color-dark($dark-gray4);
                 }
             }
         }
@@ -293,10 +388,12 @@ $context-panel-color: #aaeeff;
             box-sizing: border-box;
             margin-left: -.5em;
             padding-left: .5em - $border-indicator-width;
-            border-left: $border-indicator-width solid white;
+            border-left: $border-indicator-width solid $light-bg;
+            @include border-color-dark($dark-bg);
 
             &:hover {
-                background: $pln-hover-color;
+                background: mix($light-pln-bg, $light-fg, $hover-dark-amt);
+                @include background-dark(mix($dark-pln-bg, $dark-fg, $hover-dark-amt));
 
                 & ~ .r .annotate.long {
                     display: block;
@@ -305,7 +402,8 @@ $context-panel-color: #aaeeff;
 
             // Syntax coloring
             .com {
-                color: green;
+                color: $light-token-com;
+                @include color-dark($dark-token-com);
                 font-style: italic;
                 line-height: 1px;
             }
@@ -314,62 +412,71 @@ $context-panel-color: #aaeeff;
                 line-height: 1px;
             }
             .str {
-                color: #000080;
+                color: $light-token-str;
+                @include color-dark($dark-token-str);
             }
         }
 
         &.mis {
             .t {
-                border-left: $border-indicator-width solid #ff0000;
+                border-left: $border-indicator-width solid $mis-color;
             }
 
             &.show_mis .t {
-                background: $mis-color;
+                background: $light-mis-bg;
+                @include background-dark($dark-mis-bg);
 
                 &:hover {
-                    background: $mis-hover-color;
+                    background: mix($light-mis-bg, $light-fg, $hover-dark-amt);
+                    @include background-dark(mix($dark-mis-bg, $dark-fg, $hover-dark-amt));
                 }
             }
         }
 
         &.run {
             .t {
-                border-left: $border-indicator-width solid #00ff00;
+                border-left: $border-indicator-width solid $run-color;
             }
 
             &.show_run .t {
-                background: $run-color;
+                background: $light-run-bg;
+                @include background-dark($dark-run-bg);
 
                 &:hover {
-                    background: $run-hover-color;
+                    background: mix($light-run-bg, $light-fg, $hover-dark-amt);
+                    @include background-dark(mix($dark-run-bg, $dark-fg, $hover-dark-amt));
                 }
             }
         }
 
         &.exc {
             .t {
-                border-left: $border-indicator-width solid #808080;
+                border-left: $border-indicator-width solid $exc-color;
             }
 
             &.show_exc .t {
-                background: $exc-color;
+                background: $light-exc-bg;
+                @include background-dark($dark-exc-bg);
 
                 &:hover {
-                    background: $exc-hover-color;
+                    background: mix($light-exc-bg, $light-fg, $hover-dark-amt);
+                    @include background-dark(mix($dark-exc-bg, $dark-fg, $hover-dark-amt));
                 }
             }
         }
 
         &.par {
             .t {
-                border-left: $border-indicator-width solid #eeee99;
+                border-left: $border-indicator-width solid $par-color;
             }
 
             &.show_par .t {
-                background: $par-color;
+                background: $light-par-bg;
+                @include background-dark($dark-par-bg);
 
                 &:hover {
-                    background: $par-hover-color;
+                    background: mix($light-par-bg, $light-fg, $hover-dark-amt);
+                    @include background-dark(mix($dark-par-bg, $dark-fg, $hover-dark-amt));
                 }
             }
 
@@ -379,12 +486,13 @@ $context-panel-color: #aaeeff;
             position: absolute;
             top: 0;
             right: 2.5em;
-            font-family: verdana, sans-serif;
+            font-family: $font-normal;
         }
 
         .annotate {
-            font-family: georgia;
-            color: #666;
+            font-family: $font-normal;
+            color: $light-gray5;
+            @include color-dark($dark-gray6);
             padding-right: .5em;
 
             &.short:hover ~ .long {
@@ -432,7 +540,8 @@ $context-panel-color: #aaeeff;
         }
 
         label.ctx {
-            color: #999;
+            color: $light-gray4;
+            @include color-dark($dark-gray4);
             display: inline-block;
             padding: 0 .5em;
             font-size: .8333em;   // 10/12
@@ -444,7 +553,7 @@ $context-panel-color: #aaeeff;
             overflow-y: hidden;
             transition: all .2s;
             padding: 0 .5em;
-            font-family: verdana, sans-serif;
+            font-family: $font-normal;
             white-space: nowrap;
             background: $context-panel-color;
             border-radius: .25em;
@@ -460,11 +569,15 @@ $context-panel-color: #aaeeff;
 
 // index styles
 #index {
+    font-family: $font-code;
+    font-size: 0.875em;
+
     td, th {
         text-align: right;
         width: 5em;
         padding: .25em .5em;
-        border-bottom: 1px solid #eee;
+        border-bottom: 1px solid $light-gray2;
+        @include border-color-dark($dark-gray2);
         &.left {
             padding-left: 0;
         }
@@ -478,17 +591,17 @@ $context-panel-color: #aaeeff;
     }
     th {
         font-style: italic;
-        color: #333;
-        border-bottom: 1px solid #ccc;
+        color: $light-gray6;
+        @include color-dark($dark-gray6);
         cursor: pointer;
         &:hover {
-            background: #eee;
-            border-bottom: 1px solid #999;
+            background: $light-gray2;
+            @include background-dark($dark-gray2);
         }
         &.headerSortDown, &.headerSortUp {
-            border-bottom: 1px solid #000;
             white-space: nowrap;
-            background: #eee;
+            background: $light-gray2;
+            @include background-dark($dark-gray2);
         }
         &.headerSortDown:after {
             content: " ↓";
@@ -499,7 +612,7 @@ $context-panel-color: #aaeeff;
     }
     td.name a {
         text-decoration: none;
-        color: #000;
+        color: inherit;
     }
 
     tr.total td,
@@ -509,10 +622,11 @@ $context-panel-color: #aaeeff;
         border-bottom: none;
     }
     tr.file:hover {
-        background: #eeeeee;
+        background: $light-gray2;
+        @include background-dark($dark-gray2);
         td.name {
             text-decoration: underline;
-            color: #000;
+            color: inherit;
         }
     }
 }
@@ -524,12 +638,15 @@ $context-panel-color: #aaeeff;
     top: 0;
     width: 16px;
     height: 100%;
-    background: white;
-    border-left: 1px solid #eee;
+    background: $light-bg;
+    border-left: 1px solid $light-gray2;
+    @include background-dark($dark-bg);
+    @include border-color-dark($dark-gray2);
     will-change: transform; // for faster scrolling of fixed element in Chrome
 
     .marker {
-        background: #ddd;
+        background: $light-gray3;
+        @include background-dark($dark-gray3);
         position: absolute;
         min-height: 3px;
         width: 100%;
diff --git a/tests/gold/html/a/a_py.html b/tests/gold/html/a/a_py.html
index 2ce524140..d534c6a34 100644
--- a/tests/gold/html/a/a_py.html
+++ b/tests/gold/html/a/a_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>a.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             3 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">1 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">1 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/b_branch/b_py.html b/tests/gold/html/b_branch/b_py.html
index ce8bb875e..67a1b83b3 100644
--- a/tests/gold/html/b_branch/b_py.html
+++ b/tests/gold/html/b_branch/b_py.html
@@ -22,10 +22,10 @@ <h1>Coverage for <b>b.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             17 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">14 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">3 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
-                <span class="par run show_par shortkey_p button_toggle_par">4 partial</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">14 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">3 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
+            <button type="button" class="par run show_par shortkey_p button_toggle_par" title="Toggle lines partially run">4 partial</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/bom/2/bom_py.html b/tests/gold/html/bom/2/bom_py.html
index 3d1c98fbd..74f4f2fee 100644
--- a/tests/gold/html/bom/2/bom_py.html
+++ b/tests/gold/html/bom/2/bom_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>bom.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             7 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">5 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">2 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">5 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">2 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/bom/bom_py.html b/tests/gold/html/bom/bom_py.html
index 635f8b514..10b84edec 100644
--- a/tests/gold/html/bom/bom_py.html
+++ b/tests/gold/html/bom/bom_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>bom.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             7 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">5 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">2 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">5 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">2 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/isolatin1/isolatin1_py.html b/tests/gold/html/isolatin1/isolatin1_py.html
index 9c12c445d..b344bad6b 100644
--- a/tests/gold/html/isolatin1/isolatin1_py.html
+++ b/tests/gold/html/isolatin1/isolatin1_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>isolatin1.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_1/m1_py.html b/tests/gold/html/omit_1/m1_py.html
index 60923930b..57584495c 100644
--- a/tests/gold/html/omit_1/m1_py.html
+++ b/tests/gold/html/omit_1/m1_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m1.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_1/m2_py.html b/tests/gold/html/omit_1/m2_py.html
index de060f321..e8c1791d5 100644
--- a/tests/gold/html/omit_1/m2_py.html
+++ b/tests/gold/html/omit_1/m2_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m2.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_1/m3_py.html b/tests/gold/html/omit_1/m3_py.html
index 76a91a4a9..e714d47f3 100644
--- a/tests/gold/html/omit_1/m3_py.html
+++ b/tests/gold/html/omit_1/m3_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m3.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_1/main_py.html b/tests/gold/html/omit_1/main_py.html
index 9f242537f..28173d12b 100644
--- a/tests/gold/html/omit_1/main_py.html
+++ b/tests/gold/html/omit_1/main_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>main.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             8 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">8 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">8 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_2/m2_py.html b/tests/gold/html/omit_2/m2_py.html
index de060f321..e8c1791d5 100644
--- a/tests/gold/html/omit_2/m2_py.html
+++ b/tests/gold/html/omit_2/m2_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m2.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_2/m3_py.html b/tests/gold/html/omit_2/m3_py.html
index 76a91a4a9..e714d47f3 100644
--- a/tests/gold/html/omit_2/m3_py.html
+++ b/tests/gold/html/omit_2/m3_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m3.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_2/main_py.html b/tests/gold/html/omit_2/main_py.html
index 9f242537f..28173d12b 100644
--- a/tests/gold/html/omit_2/main_py.html
+++ b/tests/gold/html/omit_2/main_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>main.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             8 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">8 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">8 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_3/m3_py.html b/tests/gold/html/omit_3/m3_py.html
index 76a91a4a9..e714d47f3 100644
--- a/tests/gold/html/omit_3/m3_py.html
+++ b/tests/gold/html/omit_3/m3_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m3.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_3/main_py.html b/tests/gold/html/omit_3/main_py.html
index 9f242537f..28173d12b 100644
--- a/tests/gold/html/omit_3/main_py.html
+++ b/tests/gold/html/omit_3/main_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>main.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             8 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">8 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">8 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_4/m1_py.html b/tests/gold/html/omit_4/m1_py.html
index 60923930b..57584495c 100644
--- a/tests/gold/html/omit_4/m1_py.html
+++ b/tests/gold/html/omit_4/m1_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m1.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_4/m3_py.html b/tests/gold/html/omit_4/m3_py.html
index 76a91a4a9..e714d47f3 100644
--- a/tests/gold/html/omit_4/m3_py.html
+++ b/tests/gold/html/omit_4/m3_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m3.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_4/main_py.html b/tests/gold/html/omit_4/main_py.html
index 9f242537f..28173d12b 100644
--- a/tests/gold/html/omit_4/main_py.html
+++ b/tests/gold/html/omit_4/main_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>main.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             8 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">8 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">8 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_5/m1_py.html b/tests/gold/html/omit_5/m1_py.html
index 60923930b..57584495c 100644
--- a/tests/gold/html/omit_5/m1_py.html
+++ b/tests/gold/html/omit_5/m1_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>m1.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/omit_5/main_py.html b/tests/gold/html/omit_5/main_py.html
index 9f242537f..28173d12b 100644
--- a/tests/gold/html/omit_5/main_py.html
+++ b/tests/gold/html/omit_5/main_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>main.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             8 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">8 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">8 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/other/blah_blah_other_py.html b/tests/gold/html/other/blah_blah_other_py.html
index d3a4ebfc3..8f0309d49 100644
--- a/tests/gold/html/other/blah_blah_other_py.html
+++ b/tests/gold/html/other/blah_blah_other_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>/private/var/folders/j2/gr3cj3jn63s5q8g3bjvw57hm0000gp/T/cov
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             1 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">1 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">1 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/other/here_py.html b/tests/gold/html/other/here_py.html
index df2715d6f..c2f6b5f1f 100644
--- a/tests/gold/html/other/here_py.html
+++ b/tests/gold/html/other/here_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>here.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             4 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">3 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">1 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">3 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">1 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/partial/partial_py.html b/tests/gold/html/partial/partial_py.html
index f004808a2..abd755d00 100644
--- a/tests/gold/html/partial/partial_py.html
+++ b/tests/gold/html/partial/partial_py.html
@@ -22,10 +22,10 @@ <h1>Coverage for <b>partial.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             7 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">7 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">1 excluded</span>
-                <span class="par run show_par shortkey_p button_toggle_par">1 partial</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">7 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">1 excluded</button>
+            <button type="button" class="par run show_par shortkey_p button_toggle_par" title="Toggle lines partially run">1 partial</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/styled/a_py.html b/tests/gold/html/styled/a_py.html
index 4687e4642..7b6f9dcdd 100644
--- a/tests/gold/html/styled/a_py.html
+++ b/tests/gold/html/styled/a_py.html
@@ -23,9 +23,9 @@ <h1>Coverage for <b>a.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             3 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">1 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">1 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>
diff --git a/tests/gold/html/styled/style.css b/tests/gold/html/styled/style.css
index e8ff57657..ab9dbcb9d 100644
--- a/tests/gold/html/styled/style.css
+++ b/tests/gold/html/styled/style.css
@@ -4,11 +4,17 @@
 /* Don't edit this .css file. Edit the .scss file instead! */
 html, body, h1, h2, h3, p, table, td, th { margin: 0; padding: 0; border: 0; font-weight: inherit; font-style: inherit; font-size: 100%; font-family: inherit; vertical-align: baseline; }
 
-body { font-family: georgia, serif; font-size: 1em; }
+body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; font-size: 1em; background: #fff; color: #000; }
+
+@media (prefers-color-scheme: dark) { body { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { body { color: #eee; } }
 
 html > body { font-size: 16px; }
 
-p { font-size: .75em; line-height: 1.33333333em; }
+a:active, a:focus { outline: 2px dashed #007acc; }
+
+p { font-size: .875em; line-height: 1.4em; }
 
 table { border-collapse: collapse; }
 
@@ -19,15 +25,22 @@ table tr.hidden { display: none !important; }
 p#no_rows { display: none; font-size: 1.2em; }
 
 a.nav { text-decoration: none; color: inherit; }
+
 a.nav:hover { text-decoration: underline; color: inherit; }
 
 #header { background: #f8f8f8; width: 100%; border-bottom: 1px solid #eee; }
 
+@media (prefers-color-scheme: dark) { #header { background: black; } }
+
+@media (prefers-color-scheme: dark) { #header { border-color: #333; } }
+
 .indexfile #footer { margin: 1em 3em; }
 
 .pyfile #footer { margin: 1em 1em; }
 
-#footer .content { padding: 0; font-size: 85%; font-family: verdana, sans-serif; color: #666666; font-style: italic; }
+#footer .content { padding: 0; color: #666; font-style: italic; }
+
+@media (prefers-color-scheme: dark) { #footer .content { color: #aaa; } }
 
 #index { margin: 1em 0 0 3em; }
 
@@ -35,90 +48,236 @@ a.nav:hover { text-decoration: underline; color: inherit; }
 
 h1 { font-size: 1.25em; display: inline-block; }
 
-#filter_container { display: inline-block; float: right; margin: 0 2em 0 0; }
-#filter_container input { width: 10em; }
+#filter_container { float: right; margin: 0 2em 0 0; }
+
+#filter_container input { width: 10em; padding: 0.2em 0.5em; border: 2px solid #ccc; background: #fff; color: #000; }
+
+@media (prefers-color-scheme: dark) { #filter_container input { border-color: #444; } }
+
+@media (prefers-color-scheme: dark) { #filter_container input { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { #filter_container input { color: #eee; } }
+
+#filter_container input:focus { border-color: #007acc; }
 
 h2.stats { margin-top: .5em; font-size: 1em; }
 
-.stats span { border: 1px solid; border-radius: .1em; padding: .1em .5em; margin: 0 .1em; cursor: pointer; border-color: #ccc #999 #999 #ccc; }
-.stats span.run { background: #eeffee; }
-.stats span.run.show_run { border-color: #999 #ccc #ccc #999; background: #ddffdd; }
-.stats span.mis { background: #ffeeee; }
-.stats span.mis.show_mis { border-color: #999 #ccc #ccc #999; background: #ffdddd; }
-.stats span.exc { background: #f7f7f7; }
-.stats span.exc.show_exc { border-color: #999 #ccc #ccc #999; background: #eeeeee; }
-.stats span.par { background: #ffffd5; }
-.stats span.par.show_par { border-color: #999 #ccc #ccc #999; background: #ffffaa; }
+.stats button { font-family: inherit; font-size: inherit; border: 2px solid; border-radius: .1em; color: inherit; padding: .1em .5em; margin: 0 .1em; cursor: pointer; border-color: #ccc; }
+
+@media (prefers-color-scheme: dark) { .stats button { border-color: #444; } }
+
+.stats button:active, .stats button:focus { outline: 2px dashed #007acc; }
+
+.stats button:active, .stats button:focus { outline: 2px dashed #007acc; }
+
+.stats button.run { background: #eeffee; }
+
+@media (prefers-color-scheme: dark) { .stats button.run { background: #373d29; } }
+
+.stats button.run.show_run { background: #dfd; border-color: #00dd00; }
+
+@media (prefers-color-scheme: dark) { .stats button.run.show_run { background: #373d29; } }
+
+.stats button.mis { background: #ffeeee; }
+
+@media (prefers-color-scheme: dark) { .stats button.mis { background: #4b1818; } }
+
+.stats button.mis.show_mis { background: #fdd; border-color: #ff0000; }
+
+@media (prefers-color-scheme: dark) { .stats button.mis.show_mis { background: #4b1818; } }
+
+.stats button.exc { background: #f7f7f7; }
+
+@media (prefers-color-scheme: dark) { .stats button.exc { background: #333; } }
+
+.stats button.exc.show_exc { background: #eee; border-color: #808080; }
+
+@media (prefers-color-scheme: dark) { .stats button.exc.show_exc { background: #333; } }
+
+.stats button.par { background: #ffffd5; }
 
-#source p .annotate.long, .help_panel { display: none; position: absolute; z-index: 999; background: #ffffcc; border: 1px solid #888; border-radius: .2em; box-shadow: #cccccc .2em .2em .2em; color: #333; padding: .25em .5em; }
+@media (prefers-color-scheme: dark) { .stats button.par { background: #650; } }
+
+.stats button.par.show_par { background: #ffa; border-color: #dddd00; }
+
+@media (prefers-color-scheme: dark) { .stats button.par.show_par { background: #650; } }
+
+.help_panel, #source p .annotate.long { display: none; position: absolute; z-index: 999; background: #ffffcc; border: 1px solid #888; border-radius: .2em; color: #333; padding: .25em .5em; }
 
 #source p .annotate.long { white-space: normal; float: right; top: 1.75em; right: 1em; height: auto; }
 
 #keyboard_icon { float: right; margin: 5px; cursor: pointer; }
 
 .help_panel { padding: .5em; border: 1px solid #883; }
+
 .help_panel .legend { font-style: italic; margin-bottom: 1em; }
-.indexfile .help_panel { width: 20em; height: 4em; }
-.pyfile .help_panel { width: 16em; height: 8em; }
+
+.indexfile .help_panel { width: 20em; min-height: 4em; }
+
+.pyfile .help_panel { width: 16em; min-height: 8em; }
 
 #panel_icon { float: right; cursor: pointer; }
 
 .keyhelp { margin: .75em; }
-.keyhelp .key { border: 1px solid black; border-color: #888 #333 #333 #888; padding: .1em .35em; font-family: monospace; font-weight: bold; background: #eee; }
 
-#source { padding: 1em 0 1em 3rem; font-family: Consolas, "Liberation Mono", Menlo, Courier, monospace; }
+.keyhelp .key { border: 1px solid black; border-color: #888 #333 #333 #888; padding: .1em .35em; font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; font-weight: bold; background: #eee; }
+
+#source { padding: 1em 0 1em 3rem; font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; }
+
 #source p { position: relative; white-space: pre; }
+
 #source p * { box-sizing: border-box; }
-#source p .n { float: left; text-align: right; width: 3rem; box-sizing: border-box; margin-left: -3rem; padding-right: 1em; color: #999999; font-family: verdana, sans-serif; }
-#source p .n a { text-decoration: none; color: #999999; font-size: .8333em; line-height: 1em; }
-#source p .n a:hover { text-decoration: underline; color: #999999; }
+
+#source p .n { float: left; text-align: right; width: 3rem; box-sizing: border-box; margin-left: -3rem; padding-right: 1em; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n { color: #777; } }
+
+#source p .n a { text-decoration: none; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n a { color: #777; } }
+
+#source p .n a:hover { text-decoration: underline; color: #999; }
+
+@media (prefers-color-scheme: dark) { #source p .n a:hover { color: #777; } }
+
 #source p.highlight .n { background: #ffdd00; }
-#source p .t { display: inline-block; width: 100%; box-sizing: border-box; margin-left: -.5em; padding-left: 0.3em; border-left: 0.2em solid white; }
+
+#source p .t { display: inline-block; width: 100%; box-sizing: border-box; margin-left: -.5em; padding-left: 0.3em; border-left: 0.2em solid #fff; }
+
+@media (prefers-color-scheme: dark) { #source p .t { border-color: #1e1e1e; } }
+
 #source p .t:hover { background: #f2f2f2; }
+
+@media (prefers-color-scheme: dark) { #source p .t:hover { background: #282828; } }
+
 #source p .t:hover ~ .r .annotate.long { display: block; }
-#source p .t .com { color: green; font-style: italic; line-height: 1px; }
+
+#source p .t .com { color: #008000; font-style: italic; line-height: 1px; }
+
+@media (prefers-color-scheme: dark) { #source p .t .com { color: #6A9955; } }
+
 #source p .t .key { font-weight: bold; line-height: 1px; }
-#source p .t .str { color: #000080; }
+
+#source p .t .str { color: #0451A5; }
+
+@media (prefers-color-scheme: dark) { #source p .t .str { color: #9CDCFE; } }
+
 #source p.mis .t { border-left: 0.2em solid #ff0000; }
-#source p.mis.show_mis .t { background: #ffdddd; }
+
+#source p.mis.show_mis .t { background: #fdd; }
+
+@media (prefers-color-scheme: dark) { #source p.mis.show_mis .t { background: #4b1818; } }
+
 #source p.mis.show_mis .t:hover { background: #f2d2d2; }
-#source p.run .t { border-left: 0.2em solid #00ff00; }
-#source p.run.show_run .t { background: #ddffdd; }
+
+@media (prefers-color-scheme: dark) { #source p.mis.show_mis .t:hover { background: #532323; } }
+
+#source p.run .t { border-left: 0.2em solid #00dd00; }
+
+#source p.run.show_run .t { background: #dfd; }
+
+@media (prefers-color-scheme: dark) { #source p.run.show_run .t { background: #373d29; } }
+
 #source p.run.show_run .t:hover { background: #d2f2d2; }
+
+@media (prefers-color-scheme: dark) { #source p.run.show_run .t:hover { background: #404633; } }
+
 #source p.exc .t { border-left: 0.2em solid #808080; }
-#source p.exc.show_exc .t { background: #eeeeee; }
+
+#source p.exc.show_exc .t { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #source p.exc.show_exc .t { background: #333; } }
+
 #source p.exc.show_exc .t:hover { background: #e2e2e2; }
-#source p.par .t { border-left: 0.2em solid #eeee99; }
-#source p.par.show_par .t { background: #ffffaa; }
+
+@media (prefers-color-scheme: dark) { #source p.exc.show_exc .t:hover { background: #3c3c3c; } }
+
+#source p.par .t { border-left: 0.2em solid #dddd00; }
+
+#source p.par.show_par .t { background: #ffa; }
+
+@media (prefers-color-scheme: dark) { #source p.par.show_par .t { background: #650; } }
+
 #source p.par.show_par .t:hover { background: #f2f2a2; }
-#source p .r { position: absolute; top: 0; right: 2.5em; font-family: verdana, sans-serif; }
-#source p .annotate { font-family: georgia; color: #666; padding-right: .5em; }
+
+@media (prefers-color-scheme: dark) { #source p.par.show_par .t:hover { background: #6d5d0c; } }
+
+#source p .r { position: absolute; top: 0; right: 2.5em; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; }
+
+#source p .annotate { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; color: #666; padding-right: .5em; }
+
+@media (prefers-color-scheme: dark) { #source p .annotate { color: #ddd; } }
+
 #source p .annotate.short:hover ~ .long { display: block; }
+
 #source p .annotate.long { width: 30em; right: 2.5em; }
+
 #source p input { display: none; }
+
 #source p input ~ .r label.ctx { cursor: pointer; border-radius: .25em; }
+
 #source p input ~ .r label.ctx::before { content: "▶ "; }
+
 #source p input ~ .r label.ctx:hover { background: #d5f7ff; color: #666; }
+
 #source p input:checked ~ .r label.ctx { background: #aaeeff; color: #666; border-radius: .75em .75em 0 0; padding: 0 .5em; margin: -.25em 0; }
+
 #source p input:checked ~ .r label.ctx::before { content: "▼ "; }
+
 #source p input:checked ~ .ctxs { padding: .25em .5em; overflow-y: scroll; max-height: 10.5em; }
+
 #source p label.ctx { color: #999; display: inline-block; padding: 0 .5em; font-size: .8333em; }
-#source p .ctxs { display: block; max-height: 0; overflow-y: hidden; transition: all .2s; padding: 0 .5em; font-family: verdana, sans-serif; white-space: nowrap; background: #aaeeff; border-radius: .25em; margin-right: 1.75em; }
+
+@media (prefers-color-scheme: dark) { #source p label.ctx { color: #777; } }
+
+#source p .ctxs { display: block; max-height: 0; overflow-y: hidden; transition: all .2s; padding: 0 .5em; font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Ubuntu, Cantarell, "Helvetica Neue", sans-serif; white-space: nowrap; background: #aaeeff; border-radius: .25em; margin-right: 1.75em; }
+
 #source p .ctxs span { display: block; text-align: right; }
 
+#index { font-family: SFMono-Regular, Menlo, Monaco, Consolas, monospace; font-size: 0.875em; }
+
 #index td, #index th { text-align: right; width: 5em; padding: .25em .5em; border-bottom: 1px solid #eee; }
+
+@media (prefers-color-scheme: dark) { #index td, #index th { border-color: #333; } }
+
 #index td.left, #index th.left { padding-left: 0; }
+
 #index td.right, #index th.right { padding-right: 0; }
+
 #index td.name, #index th.name { text-align: left; width: auto; }
-#index th { font-style: italic; color: #333; border-bottom: 1px solid #ccc; cursor: pointer; }
-#index th:hover { background: #eee; border-bottom: 1px solid #999; }
-#index th.headerSortDown, #index th.headerSortUp { border-bottom: 1px solid #000; white-space: nowrap; background: #eee; }
+
+#index th { font-style: italic; color: #333; cursor: pointer; }
+
+@media (prefers-color-scheme: dark) { #index th { color: #ddd; } }
+
+#index th:hover { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index th:hover { background: #333; } }
+
+#index th.headerSortDown, #index th.headerSortUp { white-space: nowrap; background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index th.headerSortDown, #index th.headerSortUp { background: #333; } }
+
 #index th.headerSortDown:after { content: " ↓"; }
+
 #index th.headerSortUp:after { content: " ↑"; }
-#index td.name a { text-decoration: none; color: #000; }
+
+#index td.name a { text-decoration: none; color: inherit; }
+
 #index tr.total td, #index tr.total_dynamic td { font-weight: bold; border-top: 1px solid #ccc; border-bottom: none; }
-#index tr.file:hover { background: #eeeeee; }
-#index tr.file:hover td.name { text-decoration: underline; color: #000; }
 
-#scroll_marker { position: fixed; right: 0; top: 0; width: 16px; height: 100%; background: white; border-left: 1px solid #eee; will-change: transform; }
-#scroll_marker .marker { background: #ddd; position: absolute; min-height: 3px; width: 100%; }
+#index tr.file:hover { background: #eee; }
+
+@media (prefers-color-scheme: dark) { #index tr.file:hover { background: #333; } }
+
+#index tr.file:hover td.name { text-decoration: underline; color: inherit; }
+
+#scroll_marker { position: fixed; right: 0; top: 0; width: 16px; height: 100%; background: #fff; border-left: 1px solid #eee; will-change: transform; }
+
+@media (prefers-color-scheme: dark) { #scroll_marker { background: #1e1e1e; } }
+
+@media (prefers-color-scheme: dark) { #scroll_marker { border-color: #333; } }
+
+#scroll_marker .marker { background: #ccc; position: absolute; min-height: 3px; width: 100%; }
+
+@media (prefers-color-scheme: dark) { #scroll_marker .marker { background: #444; } }
diff --git a/tests/gold/html/unicode/unicode_py.html b/tests/gold/html/unicode/unicode_py.html
index 467229616..a4218bcc9 100644
--- a/tests/gold/html/unicode/unicode_py.html
+++ b/tests/gold/html/unicode/unicode_py.html
@@ -22,9 +22,9 @@ <h1>Coverage for <b>unicode.py</b> :
         <img id="keyboard_icon" src="keybd_closed.png" alt="Show keyboard shortcuts" />
         <h2 class="stats">
             2 statements &nbsp;
-            <span class="run shortkey_r button_toggle_run">2 run</span>
-            <span class="mis show_mis shortkey_m button_toggle_mis">0 missing</span>
-            <span class="exc show_exc shortkey_x button_toggle_exc">0 excluded</span>
+            <button type="button" class="run shortkey_r button_toggle_run" title="Toggle lines run">2 run</button>
+            <button type="button" class="mis show_mis shortkey_m button_toggle_mis" title="Toggle lines missing">0 missing</button>
+            <button type="button" class="exc show_exc shortkey_x button_toggle_exc" title="Toggle lines excluded">0 excluded</button>
         </h2>
     </div>
 </div>