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Routines |
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The handler for entity types 12 to 15, which are the domes. A dome is the slower of the two types of enemy that wander about at random; it can take up to 32 steps in a frame.
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| MoveDome | 43059 | CALL NextSpriteNumber | Move on to the next sprite using NextSpriteNumber. | |||||
| 43062 | CALL RemoveDistantEntity | Remove the entity if it is far from the camera using RemoveDistantEntity. | ||||||
| 43065 | CALL GetPosition | Fetch the position of the entity. | ||||||
| 43068 | LD B,32 | The dome can take up to 32 steps in this frame. | ||||||
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This entry point is used by the routine at MoveSaucer.
This entry point is shared by both kinds of enemy.
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| MoveEnemy_Step | 43070 | CALL TryMove | Take a step using TryMove. | |||||
| 43073 | JR NZ,MoveEnemy_Turn | Jump if the enemy has been blocked. | ||||||
| 43075 | CALL CheckEnemyOverlap | Check whether the enemy has run into another entity using CheckEnemyOverlap. | ||||||
| 43078 | JR C,MoveEnemy_Collide | Jump if it has, to turn it round. | ||||||
| 43080 | LD A,E | Jump if the enemy is not at the start of a cell. | ||||||
| 43081 | OR L | |||||||
| 43082 | JR NZ,MoveEnemy_Store | |||||||
| 43084 | LD A,(IX+7) | Fetch the time and direction of the enemy... | ||||||
| 43087 | SUB 16 | ...take away one cell... | ||||||
| 43089 | LD (IX+7),A | ...and store it. | ||||||
| 43092 | AND 240 | Jump to choose a new direction if the time has run out. | ||||||
| 43094 | JR Z,MoveEnemy_Turn | |||||||
| 43096 | LD A,B | Loop back to take another step if there are steps left. | ||||||
| 43097 | AND A | |||||||
| 43098 | JR NZ,MoveEnemy_Step | |||||||
| MoveEnemy_Store | 43100 | CALL SetPosition | Store the position of the enemy using SetPosition. | |||||
| 43103 | JP AddEntity | Jump to AddEntity. | ||||||
| MoveEnemy_Turn | 43106 | LD A,(IX+7) | Fetch the time and direction of the enemy... | |||||
| 43109 | AND 15 | ...keep the direction only... | ||||||
| 43111 | LD (IX+7),A | ...and store it. | ||||||
| 43114 | LD A,(38421) | Fetch the frame counter... | ||||||
| 43117 | AND 3 | ...and use it as a random direction. | ||||||
| 43119 | CP (IX+7) | Compare it with the current direction. | ||||||
| 43122 | JR NZ,MoveDome_NewDirection | Jump if they are different. | ||||||
| 43124 | INC A | Otherwise turn a quarter of a turn. | ||||||
| 43125 | AND 3 | Keep the direction within four. | ||||||
| MoveDome_NewDirection | 43127 | LD C,A | Keep the new direction. | |||||
| 43128 | LD A,(38423) | Fetch the random number... | ||||||
| 43131 | AND 240 | ...and use the upper bits as the time to keep going in this direction. | ||||||
| 43133 | JR NZ,MoveDome_SetTime | |||||||
| 43135 | OR 16 | Use a time of one cell if that is zero. | ||||||
| MoveDome_SetTime | 43137 | OR C | Combine the time with the new direction... | |||||
| 43138 | LD (IX+7),A | ...and store them. | ||||||
| 43141 | JR MoveEnemy_Store | Jump back to store the position. | ||||||
| MoveEnemy_Collide | 43143 | CALL ReverseDirection | Turn the enemy round using ReverseDirection. | |||||
| 43146 | CALL AddEntity | Draw it using AddEntity. | ||||||
| 43149 | RET NC | Return if it is off the screen. | ||||||
| 43150 | JP MakeBumpSound | Make the sound of a bump using MakeBumpSound. | ||||||
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