58 lines
2.6 KiB
Markdown
58 lines
2.6 KiB
Markdown
# Physics Kernel Workshop
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A from-scratch, test-driven path to a working 2D **swept collision** engine —
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the same kind that lives in `nage`, but stripped of rendering, scenes, ECS, and
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every other distraction. Just the physics, one tiny step at a time.
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## How it works (LeetCode style)
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Each folder under `steps/` is one self-contained kata:
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- `README.md` — the concept (taught from zero) and the task.
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- a stub file — the function(s) **you** implement. They start by `throw`ing.
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- a `*.test.ts` file — the validator. Red until you implement it, green when you're done.
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- sometimes a `given.ts` — prerequisites from earlier steps, already finished, so
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you only ever implement the **one new idea** of this step.
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### Run one step
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From the project root:
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```sh
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bun test workshop/steps/01-vectors
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```
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Red (failing) is the starting state. Implement the stub until it goes green, then
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ping me and I'll validate + unlock the next batch.
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> Skip nothing silently, but blast through what you already know — the early steps
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> are deliberately trivial so the test loop becomes muscle memory before the hard
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> rungs.
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## The ladder
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Each rung is a concept that the real `nage` physics depends on. We climb until
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the top rung *is* a working engine.
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**Batch 1 — foundations (these files exist now):**
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- [x] `01-vectors` — vectors as pairs of numbers: add, sub, scale
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- [x] `02-vectors-length` — length, normalize (and the zero-vector trap), dot
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- [x] `03-integration` — `pos += vel * delta`, and why framerate independence matters
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- [x] `04-aabb` — axis-aligned boxes, point-in-box, box overlap (the *discrete* test)
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- [x] `05-sweep-1d` — the **entry/exit time** of a moving point against an interval. The seed of everything.
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**Batch 2 — the swept core (these files exist now):**
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- [x] `06-ray-vs-aabb` — combine two 1D sweeps into one: ray vs box, with the surface **normal**
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- [x] `07-swept-aabb` — the **Minkowski** trick: shrink the moving box to a point, reuse step 06
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**Batch 3 — response (these files exist now):**
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- [x] `08-resolve` — stop at the moment of contact (`t`), not after
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- [x] `09-slide` — subtract the into-the-wall part of velocity and keep going along the wall
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**Batch 4 — the real loop + payoff (these files exist now):**
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- [x] `10-move-and-slide` — the full loop: multiple obstacles, iteration cap (relative velocity explained)
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- [x] `11-capstone` — a canvas demo (no test — just run it and play)
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When step 11 is green you'll have re-derived your own engine's heart — and walking
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back into `sweptAABB` should feel like reading your own handwriting again.
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