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Routines |
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Used by the routines at MOVE_ARCS, MOVE_ACTOR, MOVE_BAT, MOVE_HOPPER, MOVE_FACE, MOVE_GHOST, MOVE_MUMMY, MOVE_DRACULA, MOVE_FRANKENSTEIN, MOVE_DEVIL, MOVE_WITCH, MOVE_FACING_FLYER and MOVE_HUMPBACK.
Compares the monster IX points at against the player's record at $EA90: same room, and within 12 pixels on both axes. Confirmed by breaking here and collecting IX -- it is only ever one of the eight monster records at $EE60-$EED0, tested against the fixed player address.
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| CHECK_HIT | 85B2 | LD A,($EA91) | Cheapest rejection first: a monster in another room cannot touch anything. | |||||||
| 85B5 | LD E,$00 | |||||||||
| 85B7 | CP (IX+$01) | |||||||||
| 85BA | RET NZ | |||||||||
| 85BB | LD A,($EA90) | $31 is not an arbitrary threshold: sprite codes $01-$30 are the three playable characters, sixteen codes each (see ACTOR_HANDLERS), so "non-zero and below $31" means "$EA90 currently holds a player". It reads $66 while the game is still bringing the player into the room, which is what stops them being killed before they exist. | ||||||||
| 85BE | AND A | |||||||||
| 85BF | RET Z | |||||||||
| 85C0 | CP $31 | |||||||||
| 85C2 | RET NC | |||||||||
| 85C3 | LD A,($EA93) | |dx|, via negate-if-negative rather than a signed compare. | ||||||||
| 85C6 | SUB (IX+$03) | |||||||||
| 85C9 | JP P,CHECK_HIT_0 | |||||||||
| 85CC | NEG | |||||||||
| CHECK_HIT_0 | 85CE | CP $0C | Within 12 pixels horizontally, or no hit. | |||||||
| 85D0 | RET NC | |||||||||
| 85D1 | LD A,($EA94) | The same for |dy|. | ||||||||
| 85D4 | SUB (IX+$04) | |||||||||
| 85D7 | JP P,CHECK_HIT_1 | |||||||||
| 85DA | NEG | |||||||||
| CHECK_HIT_1 | 85DC | CP $0C | ||||||||
| 85DE | RET NC | |||||||||
| 85DF | LD A,$01 | Record the hit where the caller can find it... | ||||||||
| 85E1 | LD ($EA92),A | |||||||||
| 85E4 | CALL PLAY_SOUND_CAUGHT | ...and make a noise about it. | ||||||||
| 85E7 | LD E,$01 | |||||||||
| 85E9 | RET | |||||||||
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