16384 bytes. No loader, no blocks: the MSX maps the cartridge at 0x8000-0xBFFF —page 2— and that is the whole picture of memory, with no overlays: no address means two different things at two different times.
The first sixteen bytes are the header the BIOS reads:
41 42 13 80 00 00 00 00 00 00 00 00 00 00 00 00
'A' 'B' \_ INIT = 0x8013The two letters mark an executable cartridge; of the four vectors only INIT is set —STATEMENT, DEVICE and TEXT, the BASIC ones, are zero—.
At 0x8010 there are three bytes that are neither header nor ever executed here: C3 F7 80, a ready-made jp 0x80F7. The boot code copies them to the interrupt hook, and that is where they run.
INIT (0x8013):
That empty loop is the main program. The whole game runs inside the interrupt, fifty or sixty times a second.
Everything the game keeps lives in RAM from 0xE000. The most-read addresses:
| 0xE012 | lives left |
| 0xE05F | what is being pressed, in joystick format |
| 0xE1D0-0xE1D4 | the clock, already stored as tile numbers |
| 0xE1D6-0xE1DB | the six digits of the score |
| 0xE1E6-0xE1ED | the four sound vectors |
| 0xE20E-0xE21B | the copy of the fourteen sound chip registers |
| 0xE21D-0xE220 | the 32 bits of treasures already taken |
| 0xE221 | whether the demo is running |
| 0xE222 | the screen register: the whole world fits here |
| 0xE224 / 0xE225 | the scene's variant and kind, taken from 0xE222 |
| 0xE229-0xE246 | the ten collision boxes |
| 0xE247 | how many live objects, then one pointer per object |
| 0xE26A-0xE2BD | the sprite attribute table, uploaded whole every frame |
Behind that come the object structures, packed with no gap: 0xE2BF, 0xE2D5 (the player), 0xE2ED, 0xE303, 0xE319 and 0xE32F. The player's takes 24 bytes and the other five 22, closing the chain at 0xE345.
The cartridge writes five of the video chip's eight registers: 0 and 1 (mode and screen), 3 and 4 (colour and pattern bases) and 7 (the border, 0x11: black, at 0x8036).
Registers 2, 5 and 6 are never written: they are the ones that say where the name table, the sprite attributes and the sprite patterns live, and the game writes to 0x1800, 0x1B00 and 0x3800-0x3FFF trusting the bases the BIOS left.
| 0x0000 | the tile patterns (register 4 = 0x00, at 0xB79A) |
| 0x1800 | the name table |
| 0x1B00 | the sprite attributes |
| 0x2000 | the colours (register 3 = 0x80, at 0xB794) |
| 0x3800 | the sprite patterns |
Register 1 holds 0xE2 (0x8047): 16 KB, screen and interrupt on, 16x16 sprites.
The intro runs in one screen mode and the game in another: 0xB6B2 sets register 0 to 0x02 —graphics mode 2— for the entry banner, and 0xB788 puts it back to 0x00, graphics mode 1. That is why the game's colour table is 32 bytes and not 6144: in the game's mode colour goes per group of eight tiles.
There is a 58-byte decompressor at 0xB142 that writes straight to the video port. The format: two bytes of destination address, then one-byte tokens with the counter in the low six bits —bit 7 skip N positions, bit 6 copy N literals, neither repeat the next byte N times, zero ends—.
That covers the tile and sprite patterns (0x909E-0x95FE), the nine sprite blocks of the scene handlers (0x981E-0x99AF) and the six of the intro (0xBAB2-0xBC61). Stored raw: the four 16-tile scenery sets (0x95FE-0x97FE) and seven loose sprite patterns (0x97FE-0x981E and 0x99AF-0x9A6F).
Every compressed block ends exactly where the next one starts, and that pins its size without guessing.
There is not one string of text. The only font is twelve tiles: the ten digits (0xB8-0xC1), the colon (0xC2) and the blank (0xC3), just enough for the score and the clock. Everything else that looks like text is drawing.
Not one byte unaccounted for: 9,467 of code reached by the tracer and 6,917 of data, each inside a declared range with the instruction that reads it noted alongside.
| 0x8000-0x8010 | the header |
| 0x8010-0x8013 | the three bytes copied to the interrupt hook |
| 0x8013-0x8A69 | boot, the player, collisions, the jump, the score and the lives |
| 0x8A69-0x8AFF | RAM initialisers, the class table, the jump curve and the walk scripts |
| 0x8AFF-0x8E1B | screen and sprite loading, and scene drawing |
| 0x8E1B-0x8F06 | the floor strips and the six sinking patterns |
| 0x8F06-0x9090 | the scenery cell scripts |
| 0x9090-0x909E | fourteen raw tile numbers: row 23 |
| 0x909E-0x95FE | the five big blocks of compressed graphics |
| 0x95FE-0x97FE | the four 16-tile scenery sets |
| 0x97FE-0x9A6F | the sprites: nine compressed blocks and seven raw patterns |
| 0x9A6F-0xA086 | the frame, the objects, the screen change, the score and the clock |
| 0xA086-0xA43A | the scenery tables, the four scene layouts and the 14x18 one |
| 0xA43A-0xA61A | the vine |
| 0xA61A-0xA69E | the 33 phases the vine is traced with |
| 0xA69E-0xAE90 | the object handlers and the eight scene routines |
| 0xAE90-0xAED4 | the four dispatch tables |
| 0xAED4-0xB113 | cell scripts, object templates, animation scripts and the colours |
| 0xB113-0xB393 | the video layer, the input and the sound upload |
| 0xB393-0xB6B1 | the sound table and the nine routines it installs |
| 0xB6B1-0xB9E4 | the intro and the demo |
| 0xB9E4-0xBC6D | the intro's tables and graphics |
| 0xBC6D-0xC000 | the padding up to 16 KB: 915 bytes, all zero |