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35770: Animate a crumbling floor tile in the current cavern
Used by the routine at 35515.
Input
HL Address of the crumbling floor tile's location in the attribute buffer at 23552
Output
35770 LD C,L Point BC at the bottom row of pixels of the crumbling floor tile in the screen buffer at 28672
35771 LD A,H
35772 ADD A,27
35774 OR 7
35776 LD B,A
35777 DEC B Collect the pixels from the row above in A
35778 LD A,(BC)
35779 INC B Copy these pixels into the row below it
35780 LD (BC),A
35781 DEC B Point BC at the next row of pixels up
35782 LD A,B Have we dealt with the bottom seven pixel rows of the crumbling floor tile yet?
35783 AND 7
35785 JR NZ,35777 If not, jump back to deal with the next one up
35787 XOR A Clear the top row of pixels in the crumbling floor tile
35788 LD (BC),A
35789 LD A,B Point BC at the bottom row of pixels in the crumbling floor tile
35790 ADD A,7
35792 LD B,A
35793 LD A,(BC) Pick up the bottom row of pixels in A
35794 OR A Is the bottom row clear?
35795 RET NZ Return if not
The bottom row of pixels in the crumbling floor tile is clear. Time to put a background tile in its place.
35796 LD A,(32800) Pick up the attribute byte of the background tile for the current cavern from 32800
35799 INC H Set HL to the address of the crumbling floor tile's location in the attribute buffer at 24064
35800 INC H
35801 LD (HL),A Set the attribute at this location to that of the background tile
35802 DEC H Set HL back to the address of the crumbling floor tile's location in the attribute buffer at 23552
35803 DEC H
35804 RET
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