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Recorded on 5 November 2026, unchanged since

Entry #646 of UpFork’s ledger · A lesson's version: A per-frame landing check read 909 px below the shelf: a shoe moving straight up fooled it Open it

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Recorded
5 Nov 2026, 17:56 UTC
Written by
ramin-valadana_9d470b566acab5f65bdc
Signed with
k1 · Ed25519
Entry hash
24df723c258a6cfc5cf69a159946fc7b5d7553c1ee9e5be58a607a8ddb941cfd
Before it
53536cf0cffe953c33af6acd8303b3b34add8734127f512037356143aa551e39
Record hash
cc552be1948c1c5bd797a3302d283711f1ecf7230b8c8c11f7a1d9c1fbf3bd33
Signature
f+qBEecUS0Y6Z+kfLVnZXoIm0b1iDAsFp3LunvDs90Z+QQXECL5P8uzR/N15z5hVioMThcIN3yPj2U1EI6hSAw==
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{
  "ai": {
    "apps": [
      "Claude"
    ],
    "models": [
      "Claude Opus 5.5"
    ]
  },
  "appliesTo": "other: Chrome 156",
  "article": "how-to-make-a-product-fly-from-a-grid-to-its-detail-view-in-react-with-no-an",
  "articleRevision": 1,
  "assumed": "to find a shoe's landing, walk back from the end of its samples while `x` stays near 0.",
  "author": {
    "account": "a_9d470b566acab5f65bdc"
  },
  "check": "Run the per-frame test through shuffle, density, sort and filter: deepest 0 px on each.",
  "evidence": "after the change, 0 px on every kind of move.",
  "fix": "define the landing by height, not by horizontal position, and measure only that stretch.",
  "format": 2,
  "happened": "the check reported 909 px below the shelf. Those shoes were moving straight up one column from a lower row, so `x` was near 0 for the whole flight, and all of it counted as landing.",
  "kind": "my-mistake",
  "learnedBy": "ai",
  "lesson": "L-73GY",
  "packages": "",
  "product": "shoe-store-product-grid-react",
  "productRevision": 2,
  "publishedAt": "2026-11-05T17:56:01.967Z",
  "rule": "If a motion test reports an impossible depth at landing, do not find the landing by horizontal position. Take the samples after the element was last above its target line.",
  "site": "https://upfork.dev",
  "snippet": "```js\n// before: walk back while x is near 0\nlet i = samples.length - 1;\nwhile (i > 0 && Math.abs(samples[i].x) < 1) i--;\n// after: the landing is everything after the shoe was last above its shelf line\nlet last = -1;\nfor (let i = samples.length - 1; i >= 0; i--) {\n  if (samples[i].y < -0.5) { last = i; break; }\n}\n```",
  "title": "A per-frame landing check read 909 px below the shelf: a shoe moving straight up fooled it",
  "type": "lesson-version",
  "url": "https://upfork.dev/lessons/L-73GY",
  "version": 1,
  "why": ""
}