46 lines
2.0 KiB
Markdown
46 lines
2.0 KiB
Markdown
# Step 11 — Capstone: watch your kernel run
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No test to make green here. This is the payoff. `game.js` contains the **exact
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engine you built** across steps 01–10 — the same `sweptAABB`, `slide`, and
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`moveAndSlide`, assembled into one file — wired to a canvas and the arrow keys.
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## Run it
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It's a plain HTML file with no build step. Any of these work:
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```sh
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# simplest: just open the file in a browser
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xdg-open workshop/steps/11-capstone/index.html # linux
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# or drag index.html into a browser window
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# or serve it (nicer, avoids any file:// quirks):
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bunx serve workshop/steps/11-capstone
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# then open the printed http://localhost:... URL
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```
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Arrow keys move the pink box. Run it into the border, the ledge, the pillar, the
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bar. Push diagonally into a wall and watch it **slide** along instead of sticking.
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That sliding is your step-09 `dot`-product projection. The fact that it stops
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*at* the wall instead of tunneling through, even at speed, is your step-07 swept
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detection. The clean corners are your step-10 loop running twice in one frame.
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## Make it yours (optional)
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- Open `game.js`. The top half is your kernel — read it and confirm it matches
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what you wrote. Swap in your own `moveAndSlide` from step 10 and check it feels
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identical (it will).
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- Add a wall to the `walls` array. Change `SPEED`. Make the player bigger.
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- Try **deleting the `EPSILON` backoff** (`Math.max(0, nearest.time - EPSILON)`
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→ `nearest.time`) and push into a wall. Watch it stick and jitter. Then put it
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back. Now you've *felt* why that line exists in your real engine.
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## You're back
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That's the whole climb: pairs of numbers → sweeping a point → sweeping a box via
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Minkowski → detecting the hit → stopping and sliding → the full loop → a thing you
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can play. Every rung is a function that exists, by name, inside your real
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`engine/system/physics.ts`.
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Now go open the real `sweptAABB` with fresh eyes. You know exactly what every line
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is *supposed* to do — so the two lines that don't should stand out. Happy hunting.
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