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Routines |
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Used by the routine at ChangeActorSpeeds.
Moves the actor by the speeds in bytes 04 and 05 of the actor, changing them to 02 or FE (-2) when the actor reaches the edge of the play area. Bit 0 of byte 06 is set while the actor is moving down, and bit 1 is set while it is moving right. The ID of the actor is changed between its two frames, and the sprite is then drawn in its new position.
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| MoveBouncingActor | 72A3 | LD A,(IX+$02) | Fetch the vertical co-ordinate. | |||||
| 72A6 | ADD A,(IX+$05) | Add the vertical speed. | ||||||
| 72A9 | CP $21 | Jump to MoveBouncingActor_Top if the actor has reached the top. | ||||||
| 72AB | JR C,MoveBouncingActor_Top | |||||||
| 72AD | CP $A0 | Jump to MoveBouncingActor_Bottom if the actor has reached the bottom. | ||||||
| 72AF | JR NC,MoveBouncingActor_Bottom | |||||||
| 72B1 | LD (IX+$02),A | Update the vertical co-ordinate. | ||||||
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This entry point is used by the routines at HandleCheese and SetCustardVerticalSpeed.
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| MoveBouncingActor_Horizontal | 72B4 | LD A,(IX+$01) | Fetch the horizontal co-ordinate. | |||||
| 72B7 | ADD A,(IX+$04) | Add the horizontal speed. | ||||||
| 72BA | LD (IX+$01),A | Update the horizontal co-ordinate. | ||||||
| 72BD | CP $04 | Jump to MoveBouncingActor_LeftEdge if the actor has reached the left edge. | ||||||
| 72BF | JR C,MoveBouncingActor_LeftEdge | |||||||
| 72C1 | CP $C0 | Jump to MoveBouncingActor_RightEdge if the actor has reached the right edge. | ||||||
| 72C3 | JR NC,MoveBouncingActor_RightEdge | |||||||
| MoveBouncingActor_Animate | 72C5 | INC (IX+$07) | Increase the frame counter (byte 07 of the actor) by one. | |||||
| 72C8 | LD A,(IX+$07) | Fetch the frame counter. | ||||||
| 72CB | RRA | Shift A right. | ||||||
| 72CC | AND %00000001 | Keep only bit 0. | ||||||
| 72CE | XOR (IX+$00) | Flip bit 0 of the actor ID if bit 1 of the frame counter is set. | ||||||
| 72D1 | LD (IX+$00),A | Update the actor ID. | ||||||
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This entry point is used by the routines at HandlePeel and HandleHitActor.
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| MoveBouncingActor_Draw | 72D4 | CALL DisplayEntity | Erase the sprite and draw it in its new position using DisplayEntity. | |||||
| 72D7 | JP ColourSprite | Jump to ColourSprite to colour the sprite. | ||||||
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The actor has reached the top, so make it move down.
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| MoveBouncingActor_Top | 72DA | LD (IX+$05),$02 | Set the vertical speed to 02 (moving down). | |||||
| 72DE | SET 0,(IX+$06) | Set bit 0 of byte 06 of the actor. | ||||||
| 72E2 | JR MoveBouncingActor_Horizontal | Jump to MoveBouncingActor_Horizontal. | ||||||
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The actor has reached the left edge, so make it move right.
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| MoveBouncingActor_LeftEdge | 72E4 | LD (IX+$04),$02 | Set the horizontal speed to 02 (moving right). | |||||
| 72E8 | SET 1,(IX+$06) | Set bit 1 of byte 06 of the actor. | ||||||
| 72EC | JR MoveBouncingActor_Animate | Jump to MoveBouncingActor_Animate. | ||||||
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The actor has reached the bottom, so make it move up.
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| MoveBouncingActor_Bottom | 72EE | LD (IX+$05),$FE | Set the vertical speed to FE (moving up). | |||||
| 72F2 | RES 0,(IX+$06) | Reset bit 0 of byte 06 of the actor. | ||||||
| 72F6 | JR MoveBouncingActor_Horizontal | Jump to MoveBouncingActor_Horizontal. | ||||||
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The actor has reached the right edge, so make it move left.
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| MoveBouncingActor_RightEdge | 72F8 | LD (IX+$04),$FE | Set the horizontal speed to FE (moving left). | |||||
| 72FC | RES 1,(IX+$06) | Reset bit 1 of byte 06 of the actor. | ||||||
| 7300 | JR MoveBouncingActor_Animate | Jump to MoveBouncingActor_Animate. | ||||||
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