diff --git a/gulpfile.js b/gulpfile.js
index a9b51f19e..356f31ad6 100644
--- a/gulpfile.js
+++ b/gulpfile.js
@@ -168,6 +168,7 @@ const refactoredSrc = [
   "./src/js/test/layout-emulator.js",
   "./src/js/test/poetry.js",
   "./src/js/test/today-tracker.js",
+  "./src/js/test/weak-spot.js",
   "./src/js/replay.js",
 ];
 
diff --git a/src/js/input-controller.js b/src/js/input-controller.js
index 3874c84fb..272e1e3d7 100644
--- a/src/js/input-controller.js
+++ b/src/js/input-controller.js
@@ -23,6 +23,7 @@ import * as Focus from "./focus";
 import * as ShiftTracker from "./shift-tracker";
 import * as Replay from "./replay.js";
 import * as MonkeyPower from "./monkey-power";
+import * as WeakSpot from "./weak-spot";
 
 $("#wordsInput").keypress((event) => {
   event.preventDefault();
@@ -660,6 +661,7 @@ function handleAlpha(event) {
       );
     }
   }
+  WeakSpot.updateScore(nextCharInWord, thisCharCorrect);
 
   if (thisCharCorrect) {
     Sound.playClick(Config.playSoundOnClick);
diff --git a/src/js/test/test-logic.js b/src/js/test/test-logic.js
index 44191f9f3..050b15e25 100644
--- a/src/js/test/test-logic.js
+++ b/src/js/test/test-logic.js
@@ -32,6 +32,7 @@ import * as Replay from "./replay.js";
 import * as MonkeyPower from "./monkey-power";
 import * as Poetry from "./poetry.js";
 import * as TodayTracker from "./today-tracker";
+import * as WeakSpot from "./weak-spot";
 
 let glarsesMode = false;
 
@@ -573,6 +574,8 @@ export async function init() {
           UpdateConfig.setPunctuation(false, true);
           UpdateConfig.setNumbers(false, true);
           randomWord = Misc.getASCII();
+        } else if (Config.funbox === "weakspot") {
+          randomWord = WeakSpot.getWord(wordset);
         }
 
         if (Config.punctuation) {
diff --git a/src/js/test/weak-spot.js b/src/js/test/weak-spot.js
new file mode 100644
index 000000000..24ca5834f
--- /dev/null
+++ b/src/js/test/weak-spot.js
@@ -0,0 +1,48 @@
+import * as TestStats from "./test-stats";
+
+const adjustRate = 0.02;
+const wordSamples = 20;
+
+// TODO: base these on WPM or something instead of constants
+const defaultScore = 500;
+const incorrectPenalty = 5000;
+
+let scores = {};
+
+export function updateScore(char, isCorrect) {
+  let score = 0.0;
+  const timings = TestStats.keypressTimings.spacing.array;
+  if (timings.length > 0) {
+    score += timings[timings.length - 1];
+  }
+  if (!isCorrect) {
+    score += incorrectPenalty;
+  }
+  if (!(char in scores)) {
+    scores[char] = defaultScore;
+  }
+  // Keep an exponential moving average of the score over time.
+  scores[char] = score * adjustRate + scores[char] * (1 - adjustRate);
+}
+
+export function getWord(wordset) {
+  let highScore;
+  let randomWord;
+  for (let i = 0; i < wordSamples; i++) {
+    let newWord = wordset[Math.floor(Math.random() * wordset.length)];
+    let newScore = score(newWord);
+    if (i == 0 || newScore > highScore) {
+      randomWord = newWord;
+      highScore = newScore;
+    }
+  }
+  return randomWord;
+}
+
+function score(word) {
+  let total = 0.0;
+  for (const c of word) {
+    total += c in scores ? scores[c] : defaultScore;
+  }
+  return total / word.length;
+}
diff --git a/static/funbox/_list.json b/static/funbox/_list.json
index 6b6a8d3a1..de66df4fa 100644
--- a/static/funbox/_list.json
+++ b/static/funbox/_list.json
@@ -108,6 +108,11 @@
     "name": "poetry",
     "type": "script",
     "info": "Practice typing some beautiful prose."
+  },
+  {
+    "name": "weakspot",
+    "type": "script",
+    "info": "Focus on slow and mistyped letters."
   }
 ]