If yes — it shouts “go play!” If no — it says “nah, stay in.”

That's it. That's the whole trick. One tiny yes/no decision, made by weighing a few clues and adding them up. The wild part is that scientists discovered if you chain thousands of these simple little yes/no robots together, layer after layer, each one looking at the answers from the robots before it, they can learn to recognize handwriting, tell a dog from a muffin, or even hold a conversation. One simple idea, stacked really really tall.

It was meant for K-12 students: short enough to bash through in a sitting, real enough to feel like an actual game when you were done. I called it Yet Another Word Game — YAWG, because I find the dignity of acronyms funny.

The module never went out into the wild, and I forgot about it for the better part of four years. I dusted it off this week and realized two things: first, I never included the JavaScript file in the published bundle (oops), and second, the duplicate-letter logic — the one part of the lesson that I specifically called out as worth handling carefully — was quietly broken the whole time.

This entry is the corrected version, with the fix explained. If you just want to play, here's the game:

The bug

The interesting algorithmic wrinkle in Wordle is what happens when your guess has duplicate letters. If the target is eagle and you guess eerie, the first e is in the right place (green). But the other two e's in your guess shouldn't light up at all — there's only one e in eagle, and the green one already claimed it. Real Wordle handles this. My 2022 version did not.

Here's what the original code did, paraphrased:

// for each letter in the guess, count how many times it appears in the target
var charCnt = 0;
for (var idy = 0; idy < target.length; idy++) {
  if (wordIn[idx] == target[idy]) charCnt++;
}
// then mark it orange if (count_in_target - count_in_target) >= 0
if ((letterCtr[myLetter] - charCnt >= 0) && ...) {
  guess[idx].charClass = charStyles.inWord;
}

Look at that condition. letterCtr[myLetter] is the number of times that letter appears in the target. charCnt, computed by the inner loop right above it, is also the number of times that letter appears in the target. So the test is always 0 >= 0. Every letter in your guess that appears anywhere in the target lights up orange, no matter how many times.

I'd even left a hint to past-me's confusion in the source: a commented-out helper function called charCounter, abandoned mid-thought. I clearly knew there was a problem, didn't quite see the shape of it, and shipped what I had.

The fix

The right way to think about this is as a two-pass algorithm with a letter pool. Imagine you have a little bin labeled with each letter in the target, holding tokens for each occurrence. So for eagle you've got bins like {a:1, e:2, g:1, l:1}. Greens get scored first, and each green takes a token out of its bin. Then oranges get scored — but only if the bin still has a token left.

function scoreGuess(guessWord, targetWord, targetCounts) {
  var result = [];
  var available = Object.assign({}, targetCounts); // working copy of the pool

  // Pass 1: greens. Each green consumes a token from the pool.
  for (var idx = 0; idx < guessWord.length; idx++) {
    var letter = guessWord[idx];
    if (letter === targetWord[idx]) {
      result[idx] = { letter: letter, charClass: charStyles.rightSpot };
      available[letter]--;
    } else {
      result[idx] = { letter: letter, charClass: charStyles.wrong };
    }
  }

  // Pass 2: oranges, but only if the pool still has the letter.
  for (var idx = 0; idx < guessWord.length; idx++) {
    if (result[idx].charClass === charStyles.rightSpot) continue;
    var letter = guessWord[idx];
    if (available[letter] > 0) {
      result[idx].charClass = charStyles.inWord;
      available[letter]--;
    }
  }

  return result;
}

Two passes are necessary because greens have priority. Consider the target water and the guess otter. The two t's in your guess are tempting to mark — there's a t in water, after all — but the second one is in the exact right position. If you scored left-to-right in a single pass, you'd give the first t the orange and have nothing left for the green. Doing greens first lets them claim their tokens before the oranges go shopping.

Why this is actually a nice teaching moment

I left it as a bug for so long because the lesson sort of works around the bug — most randomly chosen target words don't expose it, and a student playing for two minutes would never notice. But that's exactly the wrong reason to ship a thing. The duplicate-letter case is where the algorithm gets interesting. It's the place where you actually have to think about state, about consumption, about why one pass isn't enough.

If I were teaching this lesson again, I'd lead with the broken version deliberately. Have students play it until somebody notices the weird highlighting. Then ask: what's the rule that's being violated? How would you fix it? You'd get to the two-pass-with-pool solution by reasoning about the problem, instead of having it handed to you.

That's a better lesson than the one I almost shipped.

The full source

Here's the cleaned-up version of YAWG.js in full. Drop it next to an HTML page with two divs (output and controls) and you're playing.

// YAWG.js — Yet Another Word Game
// A small Wordle-inspired exercise. Originally written 2022, revised 2026.

var charStyles = {
  inWord:    "color:white;padding:10px 20px;margin-right:4px;background-color:orange;border:2px solid black;",
  rightSpot: "color:white;padding:10px 20px;margin-right:4px;background-color:green;border:2px solid black;",
  wrong:     "color:white;padding:10px 20px;margin-right:4px;background-color:darkslategrey;border:2px solid black;"
};

var wordList = [
  "alert", "baker", "crowd", "diver", "eagle", "flier", "ghost", "house",
  "inner", "joint", "knife", "later", "miner", "night", "octal", "place",
  "quick", "right", "scene", "timer", "under", "voice", "witch", "xenic",
  "yacht", "zebra"
];

var wordArray, turn, target, letterCtr;
var controls, input, output, button;

function scoreGuess(guessWord, targetWord, targetCounts) {
  var result = [];
  var available = Object.assign({}, targetCounts);

  for (var idx = 0; idx < guessWord.length; idx++) {
    var letter = guessWord[idx];
    if (letter === targetWord[idx]) {
      result[idx] = { letter: letter, charClass: charStyles.rightSpot };
      available[letter]--;
    } else {
      result[idx] = { letter: letter, charClass: charStyles.wrong };
    }
  }

  for (var idx = 0; idx < guessWord.length; idx++) {
    if (result[idx].charClass === charStyles.rightSpot) continue;
    var letter = guessWord[idx];
    if (available[letter] > 0) {
      result[idx].charClass = charStyles.inWord;
      available[letter]--;
    }
  }
  return result;
}

function processInput(wordIn) {
  input.value = "";
  wordIn = (wordIn || "").toLowerCase();
  if (wordIn.length !== target.length || !/^[a-z]+$/.test(wordIn)) return;

  wordArray[turn] = scoreGuess(wordIn, target, letterCtr);

  output.innerHTML = "";
  for (var idx = 0; idx < wordArray.length; idx++) {
    for (var idy = 0; idy < wordArray[idx].length; idy++) {
      output.innerHTML +=
        "<span style='" + wordArray[idx][idy].charClass + "'>" +
        wordArray[idx][idy].letter + "</span>";
    }
    output.innerHTML += "<br>";
  }

  turn++;
  var won = (wordIn === target);
  if (won) turn = 6;

  if (turn > 5) {
    var msg = won
      ? "<p>Got it!</p>"
      : "<p>The word was <strong>" + target + "</strong>.</p>";
    controls.innerHTML = msg + "<input type='button' value='Play again' onclick='initGame();' />";
  }
}

function initGame() {
  wordArray = [];
  turn = 0;
  target = wordList[Math.floor(Math.random() * wordList.length)];

  letterCtr = {};
  for (var idx = 0; idx < target.length; idx++) {
    var ch = target[idx];
    letterCtr[ch] = (letterCtr[ch] || 0) + 1;
  }

  controls = document.getElementById('controls');
  controls.innerHTML =
    "<input id='input' type='text' size='6' maxlength='5' autofocus='true' />" +
    "<button id='button'>return</button>";

  output = document.getElementById('output');
  input  = document.getElementById('input');
  button = document.getElementById('button');

  output.innerText = "";
  input.value = "";
  input.focus();

  button.addEventListener('click', function () { processInput(input.value); });
  input.addEventListener('keypress', function (event) {
    var key = event.which || event.keyCode;
    if (key === 13) processInput(input.value);
  });
}

initGame();

The cleaned-up file fixes a few smaller things along the way: the Math.round that could occasionally pick a nonexistent word from past the end of the list, the orphaned done and guesses globals that nothing was ever doing anything with, the use of the JavaScript reserved word interface as a variable name. None of those were causing visible harm, but they were the kind of low-grade smell that suggests a draft never got read again.

That's the lesson buried inside the lesson, I think. Most code that "works" works in the boring middle of its input space. The bugs live in the corners — and the corners are usually exactly where the interesting algorithm is. Worth going back to look once in a while.