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Routines |
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Generate the initial tunnel position/movement:
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| C618 | LD A,($EAB7) | Get room number | ||
| C61B | SUB $E0 | Tunnels are from room number 224 onwards, so subtract this to get tunnel number (0-31) | ||
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This section uses the tunnel number byte (1-32, stored in the A register) to generate an offset address somewhere in the ROM - base address + ( [1-31] * 32 ).
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| C61D | LD HL,$1234 | Base ROM address | ||
| C620 | LD DE,$0020 | |||
| C623 | LD B,A | |||
| C624 | ADD HL,DE | Base ROM address + (tunnel number [0-31] x 32) | ||
| C625 | DJNZ $C624 | |||
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However, the generated result in HL is immediately overwritten in the call at C62E, making the previous calculation unnecessary.
Store generated tunnel data:
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| C627 | LD ($EB44),DE | Store the 32 from earlier - see notes above. | ||
| C62B | LD ($EB46),A | Store tunnel number (room number minus 224) | ||
| C62E | CALL $E0B0 | Copy 16 bytes of game data from the data buffer at EB43 to the room item data sets at 7C00. | ||
| C631 | LD (HL),$FF | Set end-of-data byte at start of next 16 bytes data bank at 7C00 | ||
| C633 | LD ($EB72),HL | Store the data set address pointer for the next bank. | ||
| C636 | LD A,$01 | |||
| C638 | LD ($EB7E),A | Temporary counter that holds the number of tunnel boundary walls visible on screen | ||
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