diff --git a/html/ProgressHeader.html b/html/ProgressHeader.html
index 8d6b85a..d8d931b 100644
--- a/html/ProgressHeader.html
+++ b/html/ProgressHeader.html
@@ -16,6 +16,7 @@
   h3 { margin: 0; }
   table { border-spacing: 0; }
 
+  a.cell { text-decoration: none; }
   .cell {
     display: flex;
     flex-direction: column;
diff --git a/scripts/build-table b/scripts/build-table
index fbe3e70..2e42dd4 100755
--- a/scripts/build-table
+++ b/scripts/build-table
@@ -34,13 +34,14 @@ let interpColor = {|p|
 let viz = { |k, n, cell| 
   let ratio = $k / $n
   let percent = $ratio * 100 | math round --precision 1
-  let color = if $n == 0 { "gray" } else { do $interpColor $ratio }
-  let textColor = if $k == $n { "gold" } else { "white" }
+  let bgColorOpacity = if $k == 0 { 50 } else { 100 }
+  let bgColor = if ($n == 0 or $k == 0) { "gray" } else { $"color-mix\(in srgb, (do $interpColor $ratio) ($bgColorOpacity)%, transparent\)" }
+  let textColor = if $k == $n { "gold" } else if $k == 0 { "lightgray" } else { "white" }
   let isExercise = $cell.0.section == "Exercise"
   let percentStr = $"<small style=\"font-size: 0.7rem\">($percent)%</small>"
 
   $"<div class=\"cell\" style=\"
-      background-color: ($color);
+      background-color: ($bgColor);
       color: ($textColor);
     \">
     <span>($k)&nbsp;/&nbsp;($n)</span>
@@ -57,15 +58,16 @@ let vizCh = { |n, table|
   let percent = ($ratio * 100 | math round --precision 1)
   let color = if $n == 0 { "gray" } else { do $interpColor $ratio }
   let textColor = if $completed == $total { "gold" } else { "white" }
+  let url = $"https://git.mzhang.io/school/type-theory/issues/($chapters | get $n)"
 
-  $"<div data-ch=\"($n)\" class=\"cell\" style=\"
+  $"<a data-ch=\"($n)\" class=\"cell\" style=\"
       background-color: ($color);
       color: ($textColor);
-    \">
+    \" href=\"($url)\" target=\"_blank\">
     <h3>($n)</h3>
     <small>($completed) / ($total)</small>
     <small style=\"font-size: 0.5rem;\">($percent)%</small>
-  </div>" | str replace -a "\n" ""
+  </a>" | str replace -a "\n" ""
 }
 
 let vizChapter = { |n|