From a2b6ab054609441965dbbf9feca3037bc31a91ab Mon Sep 17 00:00:00 2001
From: Jared Miller <jared@smell.flowers>
Date: Sun, 1 Mar 2026 11:59:54 -0500
Subject: [PATCH] Add split-flap animation engine with staggered character
 stepping and sound

---
 index.html | 138 +++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 123 insertions(+), 15 deletions(-)

diff --git a/index.html b/index.html
index 6d3d5d6..437077c 100644
--- a/index.html
+++ b/index.html
@@ -196,8 +196,8 @@ body {
 (function() {
   'use strict';
 
-  // ─── Config ─────────────────────────────────────────────────────────
-  // Column definitions - customize per use case
+  // ─── Constants ──────────────────────────────────────────────────────
+  const CHARSET = ' ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789:.-/,&()+\u2713\u2717';
   const COLS = [
     { key: 'time',      width: 7,  header: 'TIME' },
     { key: 'type',      width: 10, header: 'TYPE' },
@@ -210,14 +210,19 @@ body {
   ];
   const TOTAL_CHARS = COLS.reduce((s, c) => s + c.width, 0);
   const MAX_ROWS = 20;
+  const FLIP_STEP_MS = 200;
+  const STAGGER_MS = 20;
   const CHAR_WIDTH = 18;
 
+  // ─── State ──────────────────────────────────────────────────────────
+  const flapChars = new Map();
+
   // ─── Flap Element Creation ─────────────────────────────────────────
   function createFlap(ch) {
     ch = ch || ' ';
     const el = document.createElement('div');
     el.className = 'flap';
-    el.dataset.char = ch;
+    flapChars.set(el, ch);
 
     const top = document.createElement('div');
     top.className = 'flap-top';
@@ -246,12 +251,115 @@ body {
     else if (ch === '\u2717') flapEl.classList.add('flap-red');
   }
 
-  // ─── Set flap character (no animation yet) ─────────────────────────
-  function setFlapChar(flapEl, ch) {
-    flapEl.dataset.char = ch;
-    flapEl.querySelector('.flap-top .flap-char').textContent = ch;
-    flapEl.querySelector('.flap-bottom .flap-char').textContent = ch;
-    applyCharColor(flapEl, ch);
+  // ─── Sound ─────────────────────────────────────────────────────────
+  const flipAudio = new Audio('/split.mp3');
+  flipAudio.loop = true;
+  flipAudio.volume = 0;
+  let fadeInterval = null;
+
+  function startFlipSound() {
+    clearInterval(fadeInterval);
+    flipAudio.currentTime = 3;
+    flipAudio.volume = 0;
+    flipAudio.play().catch(() => {});
+    const target = 0.5;
+    const step = target / 8;
+    fadeInterval = setInterval(() => {
+      flipAudio.volume = Math.min(flipAudio.volume + step, target);
+      if (flipAudio.volume >= target) clearInterval(fadeInterval);
+    }, 10);
+  }
+
+  function stopFlipSound() {
+    clearInterval(fadeInterval);
+    const step = flipAudio.volume / 12;
+    fadeInterval = setInterval(() => {
+      flipAudio.volume = Math.max(flipAudio.volume - step, 0);
+      if (flipAudio.volume <= 0) {
+        clearInterval(fadeInterval);
+        flipAudio.pause();
+      }
+    }, 10);
+  }
+
+  // ─── Batch Flip Animation Engine ────────────────────────────────────
+  const activeFlips = [];
+  let animRunning = false;
+
+  function buildSteps(oldChar, newChar) {
+    const oldIdx = CHARSET.indexOf(oldChar);
+    const newIdx = CHARSET.indexOf(newChar);
+    if (oldIdx === -1 || newIdx === -1) return [newChar];
+
+    const steps = [];
+    if (newIdx >= oldIdx) {
+      for (let i = oldIdx + 1; i <= newIdx; i++) steps.push(CHARSET[i]);
+    } else {
+      for (let i = oldIdx + 1; i < CHARSET.length; i++) steps.push(CHARSET[i]);
+      for (let i = 0; i <= newIdx; i++) steps.push(CHARSET[i]);
+    }
+    if (steps.length === 0) return [newChar];
+
+    const maxSteps = 12;
+    if (steps.length <= maxSteps) return steps;
+    const sampled = [];
+    for (let i = 0; i < maxSteps - 1; i++) {
+      sampled.push(steps[Math.floor(i * (steps.length - 1) / (maxSteps - 1))]);
+    }
+    sampled.push(steps[steps.length - 1]);
+    return sampled;
+  }
+
+  function scheduleFlip(flapEl, newChar, delay) {
+    const oldChar = flapChars.get(flapEl) || ' ';
+    if (oldChar === newChar) return;
+
+    const topSpan = flapEl.querySelector('.flap-top .flap-char');
+    const bottomSpan = flapEl.querySelector('.flap-bottom .flap-char');
+    const steps = buildSteps(oldChar, newChar);
+    const startTime = performance.now() + delay;
+
+    activeFlips.push({
+      flapEl, topSpan, bottomSpan, steps,
+      stepIdx: 0,
+      nextTime: startTime
+    });
+
+    if (!animRunning) {
+      animRunning = true;
+      startFlipSound();
+      requestAnimationFrame(animLoop);
+    }
+  }
+
+  function animLoop(timestamp) {
+    let stillActive = false;
+
+    for (let i = 0; i < activeFlips.length; i++) {
+      const flip = activeFlips[i];
+      if (flip.stepIdx >= flip.steps.length) continue;
+
+      stillActive = true;
+      if (timestamp >= flip.nextTime) {
+        const ch = flip.steps[flip.stepIdx];
+        flip.topSpan.textContent = ch;
+        flip.bottomSpan.textContent = ch;
+        flapChars.set(flip.flapEl, ch);
+        flip.stepIdx++;
+        flip.nextTime = timestamp + FLIP_STEP_MS;
+        if (flip.stepIdx >= flip.steps.length) {
+          applyCharColor(flip.flapEl, ch);
+        }
+      }
+    }
+
+    if (stillActive) {
+      requestAnimationFrame(animLoop);
+    } else {
+      activeFlips.length = 0;
+      animRunning = false;
+      stopFlipSound();
+    }
   }
 
   // ─── Row helpers ───────────────────────────────────────────────────
@@ -269,7 +377,7 @@ body {
     const flaps = rowEl.children;
     const padded = text.padEnd(flaps.length);
     for (let i = 0; i < flaps.length; i++) {
-      setFlapChar(flaps[i], padded[i]);
+      scheduleFlip(flaps[i], padded[i], i * STAGGER_MS);
     }
   }
 
@@ -296,13 +404,13 @@ body {
     if (container.children.length !== upper.length) {
       container.innerHTML = '';
       for (let i = 0; i < upper.length; i++) {
-        container.appendChild(createFlap(upper[i]));
-      }
-    } else {
-      for (let i = 0; i < upper.length; i++) {
-        setFlapChar(container.children[i], upper[i]);
+        container.appendChild(createFlap(' '));
       }
     }
+
+    for (let i = 0; i < upper.length; i++) {
+      scheduleFlip(container.children[i], upper[i], i * STAGGER_MS);
+    }
   }
 
   // ─── Format Row ───────────────────────────────────────────────────