The code

Getting started · The game · The tape · Findings · Open questions

The memory map, once everything is in place

address	what is there
`0x0190`-`0x3F4E`	the MSX layer: VRAM, keyboard, joystick, colour, tape
`0x5E00`-`0x96F0`	the game: menu, world, play, battle and panels
`0x9E00`-`0xE677`	graphics, map and tables, not one byte of code

Inside the high block, everything in its place:

address	bytes	what it is
`0x9E00`-`0xA280`	1,152	128 map tiles, of nine bytes each
`0xA2E8`-`0xB8E8`	5,632	176 battle sprites of 16×8 with a mask
`0xB8E8`-`0xC600`	—	game state tables
`0xC800`-`0xCC00`	1,024	the font: 128 eight-byte characters
`0xCC00`-`0xE400`	6,144	the map
`0xE400`-`0xE678`	632	final tables

And one thing explains an odd address: the map starts at 0xCC67 and not at 0xCC00 because immediately before it sit the 0x80 printable characters of the font. Codes >= 0x80 are map tiles, of nine bytes; codes < 0x80 are characters, of eight.

The variables live inside the instructions

This game keeps almost everything in the operands of its own ld instructions. The clock is four ld a,nn (0x831C, 0x8326, 0x8333, 0x8355); the tape loader keeps its pointer there; and battle goes as far as rewriting opcodes, not just operands: 0x8982 writes a 0xD0 (ret nc) or a 0xD8 (ret c) into 0x8AF3 so that the same routine walks one side or the other.

That forces the real control flow to be traced and every entry point to be justified, because a linear disassembly loses its footing the moment a jump table or a self-modified operand decides where to go.

How the listing was made

The game is traced whole, over the 64 KB image, because the three blocks call one another, and is only then split into three listings with different org.
The entry points the tracer cannot deduce — pushed return addresses, jump tables, self-modified operands — go in src/juego.entries, each with the instruction that justifies it.
The gaps between blocks are declared in src/juego.nocode so a stray call cannot swallow zeros as code.
make sanity crosses the 52 declared data ranges against what the tracer believes, and checks that not one tape byte is left unexplained.

The comments, measured

make densidad

listing	instructions	comments	density	weak routines
`war_loader`	379	150	39.6%	0 of 48
`war_pantalla`	14	10	71.4%	0 of 1
`war_bajo`	785	226	28.8%	0 of 96
`war_medio`	5,664	1,646	29.1%	0 of 621
total	6,844	2,032	29.7%	0 of 767

The series applies two figures, and both are met: over 22% density and no routine below 10%.

The big block, the game itself, stood at 11 comments across 5,664 instructions — 0.2% — before this pass. Reading it line by line to comment it is what turned up almost everything in Findings, starting with the fact that 0x62FF does not hold the cursor's artwork but what the cursor covers up.