Routines
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50712: Start of tunnel data setup
Generate the initial tunnel position/movement:
50712 LD A,(60087) Get room number
50715 SUB 224 Tunnels are from room number 224 onwards, so subtract this to get tunnel number (0-31)
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 ).
50717 LD HL,4660 Base ROM address
50720 LD DE,32
50723 LD B,A
50724 ADD HL,DE Base ROM address + (tunnel number [0-31] x 32)
50725 DJNZ 50724
However, the generated result in HL is immediately overwritten in the call at 50734, making the previous calculation unnecessary.
Store generated tunnel data:
50727 LD (60228),DE Store the 32 from earlier - see notes above.
50731 LD (60230),A Store tunnel number (room number minus 224)
50734 CALL 57520 Copy 16 bytes of game data from the data buffer at 60227 to the room item data sets at 31744.
50737 LD (HL),255 Set end-of-data byte at start of next 16 bytes data bank at 31744
50739 LD (60274),HL Store the data set address pointer for the next bank.
50742 LD A,1
50744 LD (60286),A Temporary counter that holds the number of tunnel boundary walls visible on screen
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