Who's that Pokémon?: fuzzy guessing + a generation filter

Fuzzy: src/lib/fuzzy.js — editDistance + closeEnough (length-scaled typo
tolerance, 0 for names ≤4 chars). submitGuess() accepts a near-miss, so
"charizrd" counts. Plus inline ghost-text completion: once the typed
prefix matches exactly one Pokémon, the rest of the name shows greyed
after the caret; → (at end), Tab or End accepts it.

Generation filter: a "Pull from" select (All / Gen 1–9, built from the
snapshot's species.generation). Choice persists in pdx.whosThat.gen;
changing it reshuffles the pool (and the completion list) and resets the
streak.

7 new unit tests for fuzzy.js (48 total).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017Ve7HLspzeG2xDPtJQ8vmu

src/lib/fuzzy.js

@@ -0,0 +1,30 @@
+/** Levenshtein edit distance between two strings. */
+export function editDistance(a, b) {
+  a = String(a);
+  b = String(b);
+  if (a === b) return 0;
+  if (!a.length) return b.length;
+  if (!b.length) return a.length;
+  let prev = Array.from({ length: b.length + 1 }, (_, i) => i);
+  for (let i = 1; i <= a.length; i++) {
+    const cur = [i];
+    for (let j = 1; j <= b.length; j++) {
+      const cost = a[i - 1] === b[j - 1] ? 0 : 1;
+      cur[j] = Math.min(prev[j] + 1, cur[j - 1] + 1, prev[j - 1] + cost);
+    }
+    prev = cur;
+  }
+  return prev[b.length];
+}
+
+/**
+ * Is `guess` close enough to `target` to count as the same word? Exact
+ * match always; otherwise a length-scaled typo tolerance (0 for very short
+ * names so "mew" ≠ "meh", up to 2 for long ones).
+ */
+export function closeEnough(guess, target) {
+  if (!guess || !target) return guess === target;
+  if (guess === target) return true;
+  const tol = target.length <= 4 ? 0 : target.length <= 7 ? 1 : 2;
+  return editDistance(guess, target) <= tol;
+}

src/store/whosThat.js

@@ -1,7 +1,7 @@
 import { createStore } from './createStore.js';
 
 /** Score-keeping for the hidden "Who's that Pokémon?" game (#/whos-that). */
-export const whosThat = createStore('pdx.whosThat', { best: 0, plays: 0, wins: 0 });
+export const whosThat = createStore('pdx.whosThat', { best: 0, plays: 0, wins: 0, gen: 0 });
 
 export function recordResult(win, streak) {
   whosThat.set((s) => ({

src/styles/layout.css

@@ -3741,6 +3741,23 @@
   max-width: 30rem;
   margin: 0 auto;
 }
+.wtp__genrow {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  margin: 2px 0 12px;
+  font-size: 0.82rem;
+  color: var(--text-dim);
+}
+.wtp__gen {
+  padding: 5px 8px;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-sm);
+  background: var(--surface);
+  color: var(--text);
+  font: inherit;
+  font-size: 0.82rem;
+}
 .wtp__score {
   display: flex;
   flex-wrap: wrap;
@@ -3811,18 +3828,44 @@
   gap: 8px;
   margin-top: 14px;
 }
-.wtp__input {
+.wtp__inputwrap {
+  position: relative;
   flex: 1 1 12rem;
-  padding: 10px 14px;
   border: 1px solid var(--border);
   border-radius: var(--radius);
   background: var(--surface);
+}
+.wtp__inputwrap:focus-within {
+  outline: 2px solid var(--accent);
+  outline-offset: 1px;
+}
+.wtp__input {
+  width: 100%;
+  padding: 10px 14px;
+  border: none;
+  background: none;
   color: var(--text);
   font: inherit;
 }
 .wtp__input:focus-visible {
-  outline: 2px solid var(--accent);
-  outline-offset: 1px;
+  outline: none;
+}
+/* Ghost completion sits under the real text; the "typed" span is
+   transparent so the visible remainder lines up after the caret. */
+.wtp__ghost {
+  position: absolute;
+  inset: 0;
+  padding: 10px 14px;
+  font: inherit;
+  white-space: pre;
+  overflow: hidden;
+  pointer-events: none;
+}
+.wtp__ghost-typed {
+  color: transparent;
+}
+.wtp__ghost-rest {
+  color: var(--text-dim);
 }
 .wtp__feedback {
   min-height: 1.4em;

src/views/WhosThatView.js

@@ -3,31 +3,70 @@ import { loadSnapshot } from '../data/snapshot.js';
 import { Sprite } from '../components/Sprite.js';
 import { whosThat, recordResult } from '../store/whosThat.js';
 import { prefersReducedMotion } from '../store/settings.js';
+import { closeEnough } from '../lib/fuzzy.js';
 
 const loose = (s) => s.toLowerCase().replace(/[^a-z0-9]/g, '');
 const pretty = (name) => name.replace(/-/g, ' ');
 
 /**
- * Hidden mini-game — reachable by the Konami code (↑↑↓↓←→←→BA) or seven
- * quick taps on the nav wordmark, and by the bare #/whos-that hash once
- * you know it. Guess the Pokémon from its silhouette.
+ * Hidden mini-game — reachable by the Konami code (↑↑↓↓←→←→BA), seven quick
+ * taps on the dex feed's game title, or the bare #/whos-that hash. Guess
+ * the Pokémon from its silhouette; a light typo tolerance and a ghost-text
+ * completion (once your prefix is unambiguous) keep the typing painless.
  */
 export async function WhosThatView() {
   const view = el('section', { class: 'view wtp' });
   const snap = await loadSnapshot();
-  const pool = snap.species;
+  const GENS = [...new Set(snap.species.map((s) => s.generation))]
+    .filter(Boolean)
+    .sort((a, b) => a - b);
+
+  let genFilter = GENS.includes(whosThat.get().gen) ? whosThat.get().gen : 0;
+  let pool = [];
+  let NAMES = [];
+  function rebuildPool() {
+    pool = genFilter ? snap.species.filter((s) => s.generation === genFilter) : snap.species;
+    NAMES = pool.map((s) => ({ loose: loose(s.name), display: pretty(s.name) }));
+  }
+  rebuildPool();
 
   let current = null;
   let revealed = false;
   let wrong = 0;
   let streak = 0;
 
+  const genSelect = el(
+    'select',
+    {
+      class: 'wtp__gen',
+      'aria-label': 'Which generations to pull from',
+      onchange: (e) => {
+        genFilter = Number(e.target.value) || 0;
+        whosThat.set((s) => ({ ...s, gen: genFilter }));
+        streak = 0;
+        rebuildPool();
+        next();
+      },
+    },
+    el('option', { value: '0', selected: genFilter === 0 }, 'All generations'),
+    ...GENS.map((g) => el('option', { value: String(g), selected: genFilter === g }, `Gen ${g}`)),
+  );
+
   const art = el('div', { class: 'wtp__art' });
   const caption = el('div', { class: 'wtp__caption' }, 'Who’s that Pokémon?');
   const hint = el('div', { class: 'wtp__hint' });
   const feedback = el('div', { class: 'wtp__feedback' });
   const scoreEl = el('div', { class: 'wtp__score' });
 
+  const ghostTyped = el('span', { class: 'wtp__ghost-typed' });
+  const ghostRest = el('span', { class: 'wtp__ghost-rest' });
+  const ghost = el(
+    'div',
+    { class: 'wtp__ghost', 'aria-hidden': 'true', hidden: true },
+    ghostTyped,
+    ghostRest,
+  );
+
   const input = el('input', {
     class: 'wtp__input',
     type: 'text',
@@ -36,10 +75,19 @@ export async function WhosThatView() {
     autocapitalize: 'off',
     autocorrect: 'off',
     spellcheck: 'false',
+    oninput: updateGhost,
     onkeydown: (e) => {
-      if (e.key === 'Enter') submitGuess();
+      if (e.key === 'Enter') {
+        submitGuess();
+        return;
+      }
+      const atEnd =
+        input.selectionStart === input.value.length && input.selectionStart === input.selectionEnd;
+      const wantsAccept = e.key === 'Tab' || e.key === 'End' || (e.key === 'ArrowRight' && atEnd);
+      if (wantsAccept && !ghost.hidden && acceptGhost()) e.preventDefault();
     },
   });
+  const inputWrap = el('div', { class: 'wtp__inputwrap' }, ghost, input);
 
   const guessBtn = el(
     'button',
@@ -53,6 +101,42 @@ export async function WhosThatView() {
   );
   const nextBtn = el('button', { class: 'button', type: 'button', onclick: next }, 'Next →');
 
+  /** The one display name whose loose form starts with what's typed, else ''. */
+  function currentCompletion() {
+    const raw = input.value;
+    if (!raw || revealed) return '';
+    const key = loose(raw);
+    if (!key) return '';
+    const hits = NAMES.filter((n) => n.loose.startsWith(key));
+    if (hits.length !== 1) return '';
+    const full = hits[0].display;
+    // Only when what's typed is a literal prefix of the pretty name — keeps
+    // us from mangling the space in "mr mime" etc.
+    if (
+      full.length <= raw.length ||
+      full.slice(0, raw.length).toLowerCase() !== raw.toLowerCase()
+    ) {
+      return '';
+    }
+    return full;
+  }
+
+  function updateGhost() {
+    const full = currentCompletion();
+    ghost.hidden = !full;
+    if (!full) return;
+    ghostTyped.textContent = input.value;
+    ghostRest.textContent = full.slice(input.value.length);
+  }
+
+  function acceptGhost() {
+    const full = currentCompletion();
+    if (!full) return false;
+    input.value = full;
+    updateGhost();
+    return true;
+  }
+
   function renderScore() {
     const s = whosThat.get();
     const pct = s.plays ? Math.round((s.wins / s.plays) * 100) : 0;
@@ -64,7 +148,7 @@ export async function WhosThatView() {
   }
 
   function syncButtons() {
-    input.hidden = revealed;
+    inputWrap.hidden = revealed;
     guessBtn.hidden = revealed;
     revealBtn.hidden = revealed;
     nextBtn.hidden = !revealed;
@@ -81,6 +165,7 @@ export async function WhosThatView() {
     feedback.textContent = '';
     feedback.className = 'wtp__feedback';
     input.value = '';
+    updateGhost();
     syncButtons();
     input.focus();
   }
@@ -88,6 +173,7 @@ export async function WhosThatView() {
   function reveal(win) {
     revealed = true;
     art.classList.add('is-revealed');
+    updateGhost();
     caption.textContent = `It’s ${pretty(current.name)}!  #${String(current.id).padStart(4, '0')}`;
     if (win) {
       streak += 1;
@@ -112,12 +198,13 @@ export async function WhosThatView() {
 
   function submitGuess() {
     if (revealed || !input.value.trim()) return;
-    if (loose(input.value) === loose(current.name)) {
+    if (closeEnough(loose(input.value), loose(current.name))) {
       reveal(true);
       return;
     }
     wrong += 1;
     input.value = '';
+    updateGhost();
     feedback.className = 'wtp__feedback is-bad';
     if (wrong === 1) {
       feedback.textContent = 'Nope — try again.';
@@ -140,11 +227,12 @@ export async function WhosThatView() {
       el('h1', {}, 'Who’s that Pokémon?'),
       el('p', {}, 'Name it from the silhouette. Three misses and it’s revealed.'),
     ),
+    el('div', { class: 'wtp__genrow' }, el('span', {}, 'Pull from'), genSelect),
     scoreEl,
     el('div', { class: 'wtp__stage' }, art),
     caption,
     hint,
-    el('div', { class: 'wtp__controls' }, input, guessBtn, revealBtn, nextBtn),
+    el('div', { class: 'wtp__controls' }, inputWrap, guessBtn, revealBtn, nextBtn),
     feedback,
   );
 

test/fuzzy.test.js

@@ -0,0 +1,32 @@
+import { describe, it, expect } from 'vitest';
+import { editDistance, closeEnough } from '../src/lib/fuzzy.js';
+
+describe('editDistance', () => {
+  it('counts insert / delete / substitute', () => {
+    expect(editDistance('', '')).toBe(0);
+    expect(editDistance('abc', 'abc')).toBe(0);
+    expect(editDistance('abc', 'ab')).toBe(1);
+    expect(editDistance('abc', 'abx')).toBe(1);
+    expect(editDistance('kitten', 'sitting')).toBe(3);
+    expect(editDistance('charizard', 'charizrd')).toBe(1);
+  });
+});
+
+describe('closeEnough', () => {
+  it('accepts a small typo on a long name', () => {
+    expect(closeEnough('charizrd', 'charizard')).toBe(true);
+    expect(closeEnough('tyraniter', 'tyranitar')).toBe(true);
+    expect(closeEnough('gardevor', 'gardevoir')).toBe(true);
+  });
+
+  it('is strict on short names', () => {
+    expect(closeEnough('meh', 'mew')).toBe(false);
+    expect(closeEnough('mow', 'muk')).toBe(false);
+    expect(closeEnough('mew', 'mew')).toBe(true);
+  });
+
+  it("won't bridge two genuinely different names", () => {
+    expect(closeEnough('pikachu', 'raichu')).toBe(false);
+    expect(closeEnough('bulbasaur', 'ivysaur')).toBe(false);
+  });
+});