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Routines |
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Used by the routines at MoveLightLeft and TurnLightHorizontally.
Tries to turn a light so that it goes up or down. If neither of the cells is part of the frame then the light is turned round, and the routine tries again, but only once.
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| TurnLightVertically | AFF6 | LD L,E | Point HL at the cell that the light is in. | |||||||
| AFF7 | LD H,D | |||||||||
| AFF8 | LD BC,$0020 | Use a row of 20 characters. | ||||||||
| AFFB | AND A | Take it off to find the cell above. | ||||||||
| AFFC | SBC HL,BC | |||||||||
| AFFE | LD A,(HL) | Fetch the attribute of the cell. | ||||||||
| AFFF | CP $48 | Jump to turn up if it is part of the frame. | ||||||||
| B001 | JR Z,SetLightUp | |||||||||
| B003 | ADD HL,BC | Move down to the cell below. | ||||||||
| B004 | ADD HL,BC | |||||||||
| B005 | LD A,(HL) | Fetch the attribute of the cell. | ||||||||
| B006 | CP $48 | Jump to turn down if it is part of the frame. | ||||||||
| B008 | JR Z,SetLightDown | |||||||||
| B00A | LD A,($9629) | Fetch the flag that says that the light has turned. | ||||||||
| B00D | AND A | Return if it has. | ||||||||
| B00E | RET NZ | |||||||||
| B00F | OR $01 | Set the flag... | ||||||||
| B011 | LD ($9629),A | ...and store it. | ||||||||
| B014 | LD A,(IX+$00) | Fetch the type of the light. | ||||||||
| B017 | XOR $08 | Turn the light round, and store it. | ||||||||
| B019 | LD (IX+$00),A | |||||||||
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