Getting started

Everything here is reproducible. The listing is not stored as a finished file you have to trust: it is generated from the cartridge, and reassembling it gives the cartridge back byte for byte.

What you need

python3        3.8 or later, no libraries
pasmo          to reassemble
z80dasm        to disassemble
make
openMSX        only for the emulator checks

The cartridge is not distributed

This repository does not ship the game. Put the ROM in the root of the project as yiear2.rom, 32,768 bytes exactly, and check it is the same one:

make comprueba

bcb41b35ec0dddfd81ee9bd46998c0ea9c9435d6292e973d46c1324cc36e6150  yiear2.rom

The whole thing

make

That runs four steps in order:

step	what it does
`listado`	traces the flow from the declared entry points and writes `src/yiear2.asm`
`verify`	reassembles it with pasmo and compares sha256 against the ROM
`sanity`	the four checks a reassembly cannot make
`test`	the repository's own tests

verify is the one that decides whether the disassembly is trustworthy:

== ensamblando src/yiear2.asm (org 0x4000) ==
  ensamblado : 32768 bytes  bcb41b35...
  original   : 32768 bytes  bcb41b35...
OK: reproducible byte a byte

What a reassembly cannot catch

Reading data as code produces the same bytes. make sanity is what catches that, and it is four separate checks:

no byte declared as data may come out as code — check_trace.py and check_datos_como_codigo.py;
no entry point may land inside a data range — check_entradas.py, nine entry points against 160 declared data ranges;
not one byte of the cartridge left unassigned — presupuesto.py, which has to add up to 32,768.

The pictures

make imagenes

tools/graficos.py and tools/figuras.py build the screens by running in Python the same scripts, mirrors and figure readers the Z80 runs. There is not one screen capture in this repository.

And the check that closes the doubt

make vram

This boots the cartridge in openMSX, lets its own demo play, dumps the 16 KB of VRAM at nine moments and subtracts the VRAM that Python built. Looking at a picture is not enough; this is.

9 pantallas cotejadas, 0 bytes distintos en las tablas estaticas

The rest of the targets

target	what it is for
`make densidad`	how much of the listing is commented, and which routines fall short
`make sonda`	which scene the cartridge is in at each emulated second
`make web`	rebuilds the pictures and regenerates this site