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Routines |
| Prev: 46100 | Up: Map | Next: 46517 |
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Used by the routine at UpdateShots.
Updates one of the shots that the ship has fired. Shots that have bit 7 of offset 21 set go to UpdateSpecialShot. A shot that is starting (with a length of zero at offset 14) is given a starting vertical position from ShipRow with a random step, and a random colour. Shots that are facing right continue at UpdateShot_Right and ones that are facing left at UpdateLeftShot.
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| UpdateShot | 46211 | LD A,(51436) | The high byte of the ship's horizontal speed. | |||||
| 46214 | LD (IX+7),A | Write the high byte of the horizontal speed. | ||||||
| 46217 | LD A,128 | A=128. | ||||||
| 46219 | LD (23589),A | The shot stops on the terrain. | ||||||
| 46222 | BIT 7,(IX+21) | Jump to UpdateSpecialShot if bit 7 of offset 21 of IX is set. | ||||||
| 46226 | JP NZ,UpdateSpecialShot | |||||||
| 46229 | LD A,1 | A=1. | ||||||
| 46231 | LD (41431),A | One row to erase. | ||||||
| 46234 | LD (41432),A | One row to draw. | ||||||
| 46237 | LD A,(IX+14) | The high byte of the vertical acceleration. | ||||||
| 46240 | AND A | Jump to UpdateShot_Right if A is not zero. | ||||||
| 46241 | JR NZ,UpdateShot_Right | |||||||
| 46243 | LD (IX+16),0 | Store 0 at offset 16 of IX. | ||||||
| 46247 | LD (IX+7),0 | Store 0 at offset 7 of IX. | ||||||
| 46251 | CALL ChooseRandomStep | Call ChooseRandomStep. | ||||||
| 46254 | LD A,(52410) | The vertical scroll speed. | ||||||
| 46257 | NEG | Negate A. | ||||||
| 46259 | ADD A,B | A gains B. | ||||||
| 46260 | LD (IX+9),B | Write the high byte of the vertical speed. | ||||||
| 46263 | LD B,A | B=A. | ||||||
| 46264 | LD A,(23608) | The ship row. | ||||||
| 46267 | ADD A,B | A gains B. | ||||||
| 46268 | LD (IX+12),A | Write the low byte of the horizontal acceleration. | ||||||
| 46271 | CALL ChooseRandomColour | Call ChooseRandomColour. | ||||||
| 46274 | CALL MoveObject | Call MoveObject. | ||||||
| 46277 | LD (IX+9),0 | Store 0 at offset 9 of IX. | ||||||
| UpdateShot_Right | 46281 | BIT 7,(IX+0) | Jump to UpdateLeftShot if bit 7 of offset 0 of IX is set. | |||||
| 46285 | JP NZ,UpdateLeftShot | |||||||
| 46288 | LD DE,46042 | The shot offsets. | ||||||
| 46291 | CALL AddShotOffset | Call AddShotOffset. | ||||||
| 46294 | CALL FindObjectScreenAddress | Call FindObjectScreenAddress. | ||||||
| 46297 | LD B,(IX+14) | The high byte of the vertical acceleration. | ||||||
| 46300 | EXX | Switch to the alternate registers. | ||||||
| 46301 | BIT 7,(IX+16) | Jump to UpdateShot_Hit if bit 7 of offset 16 of IX is set. | ||||||
| 46305 | JR NZ,UpdateShot_Hit | |||||||
| 46307 | LD A,(IX+14) | The high byte of the vertical acceleration. | ||||||
| 46310 | AND A | Jump to UpdateShot_Longer if A is not zero. | ||||||
| 46311 | JR NZ,UpdateShot_Longer | |||||||
| 46313 | LD (IX+15),8 | Store 8 at offset 15 of IX. | ||||||
| 46317 | LD (IX+11),136 | Store 136 at offset 11 of IX. | ||||||
| UpdateShot_Longer | 46321 | LD A,16 | A=16. | |||||
| 46323 | ADD A,(IX+7) | Add the byte at offset 7 of IX to A. | ||||||
| 46326 | LD (IX+7),A | Write the high byte of the horizontal speed. | ||||||
| 46329 | CALL TestShotHitsGround | Call TestShotHitsGround. | ||||||
| 46332 | JR Z,UpdateShot_Move | Jump to UpdateShot_Move if the zero flag is set. | ||||||
| 46334 | LD A,240 | A=240. | ||||||
| 46336 | ADD A,(IX+7) | Add the byte at offset 7 of IX to A. | ||||||
| 46339 | LD (IX+7),A | Write the high byte of the horizontal speed. | ||||||
| 46342 | SET 7,(IX+16) | Set bit 7 of offset 16 of IX. | ||||||
| 46346 | SET 5,(IX+16) | Set bit 5 of offset 16 of IX. | ||||||
| 46350 | JP UpdateShot_Count | Jump to UpdateShot_Count. | ||||||
| UpdateShot_Move | 46353 | LD A,8 | A=8. | |||||
| 46355 | ADD A,(IX+11) | Add the byte at offset 11 of IX to A. | ||||||
| 46358 | LD (IX+11),A | Write the high byte of the horizontal acceleration. | ||||||
| 46361 | CP 184 | Jump to UpdateShot_Length if A is not 184. | ||||||
| 46363 | JR NZ,UpdateShot_Length | |||||||
| 46365 | SET 7,(IX+16) | Set bit 7 of offset 16 of IX. | ||||||
| UpdateShot_Length | 46369 | LD A,(IX+14) | The high byte of the vertical acceleration. | |||||
| 46372 | INC A | Advance A. | ||||||
| 46373 | LD (IX+14),A | Write the high byte of the vertical acceleration. | ||||||
| 46376 | LD A,(IX+15) | The low byte of the vertical acceleration. | ||||||
| 46379 | DEC A | Step A back. | ||||||
| 46380 | LD (IX+15),A | Write the low byte of the vertical acceleration. | ||||||
| 46383 | JP UpdateShot_Table | Jump to UpdateShot_Table. | ||||||
| UpdateShot_Hit | 46386 | BIT 5,(IX+16) | Jump to UpdateShot_Stopped if bit 5 of offset 16 of IX is set. | |||||
| 46390 | JR NZ,UpdateShot_Stopped | |||||||
| 46392 | CALL TestShotHitsGround | Call TestShotHitsGround. | ||||||
| 46395 | JR Z,UpdateShot_Facing | Jump to UpdateShot_Facing if the zero flag is set. | ||||||
| 46397 | SET 5,(IX+16) | Set bit 5 of offset 16 of IX. | ||||||
| UpdateShot_Stopped | 46401 | LD A,(IX+7) | The high byte of the horizontal speed. | |||||
| 46404 | NEG | Negate A. | ||||||
| 46406 | ADD A,(IX+11) | Add the byte at offset 11 of IX to A. | ||||||
| 46409 | LD (IX+11),A | Write the high byte of the horizontal acceleration. | ||||||
| 46412 | LD (IX+7),0 | Store 0 at offset 7 of IX. | ||||||
| 46416 | BIT 6,(IX+16) | Test bit 6 of offset 16 of IX. | ||||||
| 46420 | LD B,(IX+14) | The high byte of the vertical acceleration. | ||||||
| 46423 | LD C,(IX+11) | The high byte of the horizontal acceleration. | ||||||
| 46426 | JR Z,UpdateShot_Clip | Jump to UpdateShot_Clip if the zero flag is set. | ||||||
| 46428 | DEC B | Step B back. | ||||||
| 46429 | LD A,C | A=C. | ||||||
| 46430 | ADD A,8 | Add 8 to A. | ||||||
| 46432 | LD C,A | C=A. | ||||||
| UpdateShot_Clip | 46433 | SLA B | Shift B left. | |||||
| 46435 | SLA B | Shift B left. | ||||||
| 46437 | SLA B | Shift B left. | ||||||
| 46439 | LD A,B | A=B. | ||||||
| 46440 | ADD A,C | A gains C. | ||||||
| 46441 | AND %11111000 | Keep the bits of A that are set in 248. | ||||||
| 46443 | CP 228 | Jump to UpdateShot_Facing if A is less than 228. | ||||||
| 46445 | JR C,UpdateShot_Facing | |||||||
| 46447 | CP 240 | Jump to UpdateShot_Shorten if A is less than 240. | ||||||
| 46449 | JR C,UpdateShot_Shorten | |||||||
| 46451 | LD (IX+14),0 | Store 0 at offset 14 of IX. | ||||||
| UpdateShot_Shorten | 46455 | LD A,(IX+14) | The high byte of the vertical acceleration. | |||||
| 46458 | DEC A | Step A back. | ||||||
| 46459 | LD (IX+14),A | Write the high byte of the vertical acceleration. | ||||||
| 46462 | LD A,(IX+11) | The high byte of the horizontal acceleration. | ||||||
| 46465 | SUB 8 | Subtract 8 from A. | ||||||
| 46467 | LD (IX+11),A | Write the high byte of the horizontal acceleration. | ||||||
| UpdateShot_Facing | 46470 | BIT 6,(IX+16) | Jump to UpdateShot_Count if bit 6 of offset 16 of IX is clear. | |||||
| 46474 | JR Z,UpdateShot_Count | |||||||
| 46476 | LD A,(IX+14) | The high byte of the vertical acceleration. | ||||||
| 46479 | DEC A | Step A back. | ||||||
| 46480 | LD (IX+14),A | Write the high byte of the vertical acceleration. | ||||||
| 46483 | LD A,(IX+11) | The high byte of the horizontal acceleration. | ||||||
| 46486 | ADD A,8 | Add 8 to A. | ||||||
| 46488 | LD (IX+11),A | Write the high byte of the horizontal acceleration. | ||||||
| 46491 | JR UpdateShot_Table | Jump to UpdateShot_Table. | ||||||
| UpdateShot_Count | 46493 | LD A,(IX+15) | The low byte of the vertical acceleration. | |||||
| 46496 | DEC A | Step A back. | ||||||
| 46497 | LD (IX+15),A | Write the low byte of the vertical acceleration. | ||||||
| 46500 | JR NZ,UpdateShot_Table | Jump to UpdateShot_Table if the zero flag is clear. | ||||||
| 46502 | SET 6,(IX+16) | Set bit 6 of offset 16 of IX. | ||||||
| UpdateShot_Table | 46506 | LD DE,46042 | The shot offsets. | |||||
| 46509 | JR UpdateShot_Offset | Jump to UpdateShot_Offset. | ||||||
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This entry point is used by the routine at UpdateLeftShot.
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| UpdateShot_LeftTable | 46511 | LD DE,46050 | The second shot offset. | |||||
| UpdateShot_Offset | 46514 | CALL AddShotOffset | Call AddShotOffset. | |||||
| Prev: 46100 | Up: Map | Next: 46517 |