72 lines
3.3 KiB
Markdown
72 lines
3.3 KiB
Markdown
# Rabbit Scooter — C64
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A Commodore 64 port of [rabbitroller](../rabbitroller), the Game & Watch
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style LCD mini game, written in 6502 assembly (built with the ACME
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assembler, using the same toolchain and layout as [c64-demo](../c64-demo)).
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Rabbits hop toward you on a five-lane road. Steer your scooter left and
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right to dodge them: a rabbit that reaches your lane is a **miss**, one
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that passes in any other lane is a **point**. Three misses end the round.
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The spawn rate and the rabbits' speed ramp up with your score, just like
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in the original.
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In **multiplayer** the rabbits still spawn on their own, but player 2
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steers the closest one left and right, trying to run the scooter down.
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## Controls
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| Input | Action |
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|-------|--------|
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| Menu: joystick up/down, or the `S` / `M` / `C` keys | pick single player / multiplayer / credits |
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| Menu: fire (or `SPACE`); the `1` / `2` keys pick and start at once | open the picked line |
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| P1: joystick port 2 left/right, or `A` / `D` | move the scooter (auto-repeats while held) |
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| P2: joystick port 1 left/right, or `J` / `L` | steer the closest rabbit (multiplayer) |
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| Fire (or `SPACE`) | start; on the game over screen: back to the menu |
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## How it works
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- PAL frame loop synced by polling the raster beam (no interrupts), one
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state update per frame — intro, menu, play and game over are `updvec`
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states. Boot shows the giant TTG / Teletype Games logo with the gold
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color wash from the c64-demo; the menu and the game over screens are
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full-screen cards on black — big block-letter titles, *fire = start
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game* on the menu, the final score and *fire = retry* after a loss.
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- The background is raster-split at the horizon: sky above, grass below.
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The road is a grey wedge of inverse-space characters between painted
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white edge lines, with trees along both shoulders.
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- The player is hardware sprite 0; up to seven rabbits live on sprites
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1–7. Rabbits follow the road's perspective: a linear y ramp and a t²
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horizontal fan-out, both precomputed into tables at assembly time
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(`tables.asm`). Far rabbits use small sprite frames, near ones switch
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to big frames and finally to double-sized expanded sprites.
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- Random lanes and speeds come from an 8-bit LFSR stirred with the
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free-running CIA timer.
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- Sprite art sits below `$1000` so the VIC never sees the character ROM
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shadow instead of it.
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## Files
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| File | Contents |
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|------|----------|
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| `main.asm` | BASIC stub, init, frame loop, state dispatch |
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| `defs.asm` | registers, constants, zero page, macros |
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| `intro.asm` | boot screen: giant TTG logo with the gold wash |
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| `title.asm` | full-screen menu: big logo, mode picker, hopping rabbits |
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| `credits.asm` | demo-style credits: pixel scroller, gold wash, rainbow crew, sprite parade + AI warning |
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| `play.asm` | gameplay: input, spawning, scoring, HUD |
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| `over.asm` | full-screen game over: big title, score, retry |
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| `common.asm` | shared routines: printing, road, input, RNG, rabbit positioning |
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| `tables.asm` | assembly-time perspective and speed tables |
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| `sprites.asm` | sprite art (scooter, 4+4 rabbit frames) |
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## Build & run
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```
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make deps # macOS: brew install acme vice
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make build # -> rabbit.prg
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make run # build + launch in VICE (x64sc)
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```
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The same targets are available as VS Code tasks. A test build that boots
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straight into gameplay: `acme -DAUTOPLAY=1 -f cbm -o test.prg main.asm`.
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