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Routines |
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Updates the bonus item if there is one. Otherwise, it puts a new bonus item into a cubby hole, with a chance of one in two hundred and fifty-six. The hole is chosen using the game timer, from the first ten, and has to be empty. The hole is marked with FF and the type of the bonus item is a random one of 0B 0C or 0D (with 0B more likely). It goes back to the start of the main loop at MainLoop_NewPass.
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| SpawnBonusItem | 71BE | LD A,($5E3C) | A=the state of the bonus item from State_BonusItem. | |
| 71C1 | AND A | Test the state. | ||
| 71C2 | JP NZ,UpdateBonusItem | Jump to UpdateBonusItem if there is a bonus item. | ||
| 71C5 | LD A,($5E19) | A=the random number from RandomNumber. | ||
| 71C8 | AND A | Test the random number. | ||
| 71C9 | JP NZ,MainLoop_NewPass | Jump to MainLoop_NewPass to start another pass unless it is zero. | ||
| 71CC | LD A,($5E17) | A=the game timer from GameTimer. | ||
| 71CF | AND %00001111 | Keep only bits 0-3. | ||
| 71D1 | CP $0A | Jump to MainLoop_NewPass if it is 0A or more. | ||
| 71D3 | JP NC,MainLoop_NewPass | |||
| 71D6 | LD C,A | C=the cubby hole number. | ||
| 71D7 | LD B,$00 | B=00. | ||
| 71D9 | LD HL,$5E23 | HL=CubbyHoles. | ||
| 71DC | ADD HL,BC | Add the cubby hole number. | ||
| 71DD | LD A,(HL) | A=the contents of the cubby hole. | ||
| 71DE | AND A | Test the contents. | ||
| 71DF | JP NZ,MainLoop_NewPass | Jump to MainLoop_NewPass if the cubby hole is not empty. | ||
| 71E2 | LD (HL),$FF | Write FF to the cubby hole. | ||
| 71E4 | LD IX,$5E3C | IX=State_BonusItem (the bonus item). | ||
| 71E8 | LD A,C | A=the cubby hole number. | ||
| 71E9 | CP $05 | Jump to SpawnBonusItem_Right if the cubby hole is on the right. | ||
| 71EB | JR NC,SpawnBonusItem_Right | |||
| 71ED | LD (IX+$01),$08 | Write 08 to the X position of the bonus item. | ||
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This entry point is used by the routine at SpawnBonusItem_Right.
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| SpawnBonusItem_Row | 71F1 | RRCA | Rotate the row number round so it is in bits 5-7. | |
| 71F2 | RRCA | |||
| 71F3 | RRCA | |||
| 71F4 | AND %11100000 | Keep only bits 5-7. | ||
| 71F6 | ADD A,$37 | Add 37. | ||
| 71F8 | LD (IX+$02),A | Write it to the Y position of the bonus item. | ||
| 71FB | LD A,R | A=the refresh register. | ||
| 71FD | AND %00000011 | Keep only bits 0-1. | ||
| 71FF | CP $03 | Jump to SpawnBonusItem_Type unless it is 03. | ||
| 7201 | JR NZ,SpawnBonusItem_Type | |||
| 7203 | XOR A | A=00. | ||
| SpawnBonusItem_Type | 7204 | ADD A,$0B | Add 0B to give the type of the bonus item. | |
| 7206 | LD (IX+$04),$FF | Write FF to IX+04 (the contents the cubby hole should have). | ||
| 720A | LD (IX+$00),A | Write the type to the state of the bonus item. | ||
| 720D | LD (IX+$03),$43 | Write 43 (magenta) to the colour of the bonus item. | ||
| 7211 | LD (IX+$05),C | Write the cubby hole number to IX+05. | ||
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This entry point is used by the routine at CollectBonusItem.
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| SpawnBonusItem_Tone | 7214 | CALL PlayMidTone | Play a tone using PlayMidTone. | |
| 7217 | JP MainLoop_NewPass | Jump to MainLoop_NewPass. | ||
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