64 lines
2.5 KiB
Markdown
64 lines
2.5 KiB
Markdown
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# GALAGA — a C engine with akbasic embedded as its enemy brain
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A GALAGA-style fixed shooter whose core engine is C on libakgl, with akbasic
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linked in as the scripting engine that owns every enemy's behavior. One BASIC
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script — `galaga.bas`, nothing but `DEF` functions and an `END` — is called
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once per enemy per frame through a custom `akgl_Actor` update hook. Bullets,
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collision, scoring and screens are C forever; everything an enemy *decides* is
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BASIC.
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This is the checked-in example behind two tutorial chapters, and the chapters
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are the intended way in:
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* **[Chapter 20](../../docs/20-tutorial-galaga.md)** — the engine and the
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boundary: from an empty file to a C game that boots a script and hands one
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actor to BASIC.
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* **[Chapter 21](../../docs/21-tutorial-galaga-enemies.md)** — the data
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structures and the AI: from `SELF@` to a full attacking wave.
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It is an academic exercise demonstrating *how* such an embed is done, not a
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claim that it is the best way to write a GALAGA.
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## Building and running
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The example builds when both example and graphics builds are on:
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```
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cmake -S . -B build-akgl -DAKBASIC_WITH_AKGL=ON
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cmake --build build-akgl --target akbasic_example_galaga
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build-akgl/akbasic_example_galaga
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```
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| Key | Does |
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|---|---|
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| Left / Right | move the ship |
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| Space | fire (two shots on screen, the classic rule) |
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| Return | choose a menu entry |
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## Flags
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```
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akbasic_example_galaga [--assets DIR] [--script PATH] [--frames N]
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[--autoplay] [--screenshot PATH] [--screenshot-frame N]
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```
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`--script` points at a different enemy script, which is the whole point of the
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architecture: edit `galaga.bas`, run again, no rebuild. `--frames N` with
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`--autoplay` is the headless smoke test CI runs under the dummy SDL drivers;
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the final log line reports frames, score, kills and shots per kind, and the
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script-error count — a wave of dumb enemies still exits 0, and that count is
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how you notice.
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## The files
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| File | Owns |
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| `galaga.h` | the shared structs — the whole boundary in one header |
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| `main.c` | startup order, the frame loop, screens, the starfield |
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| `script.c` | everything that touches the interpreter |
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| `enemies.c` | wave table, formation grid, the enemy update hook |
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| `player.c` | the ship, both bullet kinds, every collision |
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| `galaga.bas` | every decision an enemy makes |
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| `interop_test.c` | round-trip proof the boundary works, run by CTest |
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| `assets/` | sprite/character JSON, and Kenney CC0 art under `assets/art/` |
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