58 lines
2.1 KiB
Markdown
58 lines
2.1 KiB
Markdown
# snake6502
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*snake6502* is a snake-like game clone for Commodore home computers, written for fun because «I always wanted to code something for a computer of my retrocomputers collection – actually, this is the main reason I collect them: to write programs».
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Download the [binary .prg](dist/snake.prg).
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Current development status [here](https://git.giomba.it/giomba/snake6502).
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## Compile
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You need the GNU compiler collection and the [dasm](https://dasm-assembler.github.io/) macro assembler, then:
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```
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$ make
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```
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You can also define the following environment variables:
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```$ DEBUG=1 make``` build with debugging artifacts
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```$ VERBOSE=1 make``` output useful info during compilation
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```$ CARTRIDGE=1 make``` produces an 8K bin ready to be burnt to an *PROM
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## Developer docs
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### Memory map
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Address | PRG | Description
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----------------------|-------|------------
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```$0000 - $0001``` | no | hardware
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```$0002 - $00FF``` | no | zero page pointers
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```$0100 - $07FF``` | no | *free ram*
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```$0800 - $0FFF``` | yes | autostart (BASIC or cartridge) + Low Program Segment
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```$1000 - $1FFF``` | yes | SID tune + Middle Program Segment
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```$2000 - $27FF``` | yes | custom char
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```$2800 - $xxxx``` | yes | High Program Segment (only needed part used)
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```$xxxx - $CCFF``` | no | *free ram*
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```$CD00 - $CDFF``` | no | data segment (not-initialized vars)
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```$CE00 - $CEFF``` | no | list X
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```$CF00 - $CFFF``` | no | list Y
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```$D000 - $DFFF``` | no | I/O
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```$E000 - $FFFF``` | no | Kernal
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Note: program (code) segments have been put in all possible free spots in order to squeeze the game into an 8K cartridge.
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### Custom charset
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Index | Description
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----------------|-------------
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```$00 - $1F``` | A-Z (space first)
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```$20 - $3F``` | A-Z, reversed (space first)
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```$40 - $4F``` | hex digits
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```$50 - $5F``` | hex digits, reversed
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```$60 - ``` | game tiles
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### Cartridge
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Cartridge version is at $8000 and simply copies itself back at $800.
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Cartridge version can not be built with DEBUG=1 flag due to size constraints.
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