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8AEB: Cycle the INK and PAPER colours
Used by the routines at 87CA (while scrolling the instructions across the screen) and 89AD (while the game is paused).
8AEB LD HL,$5800 Point HL at the first byte of the attribute file
8AEE LD A,(HL) Pick up this byte
8AEF AND $07 Keep only bits 0-2 (the INK colour)
8AF1 OUT ($FE),A Set the border colour to match
Now we loop over every byte in the attribute file.
8AF3 LD A,(HL) Pick up an attribute file byte
8AF4 ADD A,$03 Cycle the INK colour forward by three
8AF6 AND $07
8AF8 LD D,A Save the new INK colour in D
8AF9 LD A,(HL) Pick up the attribute file byte again
8AFA ADD A,$18 Cycle the PAPER colour forward by three (and turn off any BRIGHT colours)
8AFE OR D Merge in the new INK colour
8AFF LD (HL),A Save the new attribute byte
8B00 INC HL Point HL at the next byte in the attribute file
8B01 LD A,H Have we reached the end of the attribute file yet?
8B02 CP $5B
8B04 JR NZ,$8AF3 If not, jump back to modify the next byte
8B06 RET
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