revert(gacha): restore the original pack tear and drop motion

Only the card rising out of the pack keeps its exponential easing; the scripted tear and the pack falling away move as pack-cards drew them.

renderer/src/gacha/page/page.css

@@ -34,26 +34,6 @@ body {
   width: min(36vh, 60vw);
 }
 
-/*
- * The torn pack keeps pack-cards' 1.35s drop and its short hold, but falls
- * in one exponential ease-in-out. Not scoped to #stage: the pack also drops
- * inside pack-cards' flight overlay on <body>.
- */
-html .recap-pack-torn :is(.recap-webgl-pack, .recap-pack-lining) {
-  animation-name: wish-pack-away;
-  animation-timing-function: cubic-bezier(0.87, 0, 0.13, 1);
-}
-
-@keyframes wish-pack-away {
-  0%,
-  20% {
-    transform: translateY(0);
-  }
-  100% {
-    transform: translateY(calc(100vh + 100%));
-  }
-}
-
 /* A video has no buttons or prompts to read: hide the interactive captions. */
 #stage .recap-pack-scene > .eyebrow,
 #stage .recap-pack-title,

renderer/src/gacha/wish-plan.js

@@ -82,23 +82,10 @@ export const getWishPageProps = (request) => {
   return {label: request.label, rank, stars: request.rarity, rarity, glow, artwork: {accent, tint}};
 };
 
-/**
- * Exponential ease-in-out over 0..1.
- *
- * @param {number} t
- */
-const easeInOutExpo = (t) => {
-  if (t <= 0 || t >= 1) {
-    return Math.min(1, Math.max(0, t));
-  }
-  return t < 0.5 ? 2 ** (20 * t - 10) / 2 : (2 - 2 ** (10 - 20 * t)) / 2;
-};
-
 /**
  * Pointer position for a frame during the drag, as fractions of the pack
  * control's box, or null outside it. The button is held while the pointer
- * sweeps across the seal, easing exponentially in and out like a hand
- * tearing it.
+ * sweeps across the seal.
  *
  * @param {number} seconds
  * @returns {{x: number, y: number} | null}
@@ -108,7 +95,7 @@ export const getDragPointer = (seconds) => {
   if (seconds < dragStart || seconds > dragEnd) {
     return null;
   }
-  return {x: 0.08 + 0.9 * easeInOutExpo((seconds - dragStart) / (dragEnd - dragStart)), y: 0.12};
+  return {x: 0.08 + 0.9 * ((seconds - dragStart) / (dragEnd - dragStart)), y: 0.12};
 };
 
 const contentTypes = Object.freeze({

renderer/test/gacha-wish-plan.test.js

@@ -46,19 +46,6 @@ describe('gacha wish plan', () => {
     expect(dragEnd + 2).toBeLessThan(gachaTotalSeconds);
   });
 
-  test('the drag eases exponentially in and out across the seal', () => {
-    const {dragStart, dragEnd} = wishTimeline;
-    const x = (/** @type {number} */ fraction) =>
-      getDragPointer(dragStart + (dragEnd - dragStart) * fraction)?.x ?? NaN;
-    expect(x(0)).toBeCloseTo(0.08);
-    expect(x(1)).toBeCloseTo(0.98);
-    expect(x(0.5)).toBeCloseTo(0.53);
-    // Slow at both ends, fast through the middle.
-    expect(x(0.2) - x(0)).toBeLessThan(0.01);
-    expect(x(1) - x(0.8)).toBeLessThan(0.01);
-    expect(x(0.6) - x(0.4)).toBeGreaterThan(0.6);
-  });
-
   test('page requests map to the page directory and the installed package', () => {
     expect(resolveWishAsset(`${wishOrigin}/index.html`, roots)).toEqual({
       file: path.join(roots.page, 'index.html'),