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Routines |
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Used by the routines at RunLife and ExplodeShip.
Does the work for one frame of the game: increases the frame counter at FrameCounter, saves the position where the ship can restart with SaveRestartPosition (every fourth frame) and clears the scroll speeds. Unless the ship is out of control, it is then moved by UpdateShipSpeeds and tested against the terrain and the map objects. The shots are moved by UpdateShots and the rest of the world by ScrollWorld, which comes back at RunFrame_Draw. Then a part that has just been collected is fitted and the ship is drawn.
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| RunFrame | 50036 | LD HL,(39524) | The frame counter. | |
| 50039 | INC HL | The next frame. | ||
| 50040 | LD (39524),HL | Write the frame counter back. | ||
| 50043 | BIT 0,L | On even frames the falling timer is left alone. | ||
| 50045 | JR Z,RunFrame_Counter | |||
| 50047 | LD A,(35183) | The falling timer. | ||
| 50050 | AND A | Leave it once it has run out. | ||
| 50051 | JR Z,RunFrame_Counter | |||
| 50053 | DEC A | One frame less on the timer. | ||
| 50054 | LD (35183),A | Write the falling timer back. | ||
| RunFrame_Counter | 50057 | LD A,L | The low byte of the frame counter. | |
| 50058 | AND %00000011 | Only the bottom two bits of the frame. | ||
| 50060 | CALL Z,SaveRestartPosition | Save the restart position every fourth frame. | ||
| 50063 | PUSH IY | Keep the pointer that was in IY. | ||
| 50065 | XOR A | The scroll starts at rest. | ||
| 50066 | LD (52411),A | No horizontal scroll yet. | ||
| 50069 | LD (52410),A | No vertical scroll yet. | ||
| 50072 | LD A,(36691) | The ship state. | ||
| 50075 | CP 11 | State 11 or more means the ship is gone. | ||
| 50077 | JR NC,RunFrame_Shots | |||
| 50079 | LD IX,51429 | The ship. | ||
| 50083 | CALL UpdateShipSpeeds | Change the ship's speeds from the controls. | ||
| 50086 | LD A,255 | The ship uses collision mode 255. | ||
| 50088 | LD (23589),A | Remember that mode for the terrain test. | ||
| 50091 | LD A,(38571) | The crystal-delivery flag. | ||
| 50094 | AND A | A delivered stack skips the terrain test. | ||
| 50095 | JR NZ,RunFrame_Shots | |||
| 50097 | CALL SetShipSpeeds | Give the ship the opposite of the scroll, so it stays put. | ||
| 50100 | LD C,48 | The ship's collision width is 48. | ||
| 50102 | LD A,(62966) | The ninth part flag. | ||
| 50105 | AND A | Is the ninth part fitted? | ||
| 50106 | LD B,4 | Four extra rows of height without that part. | ||
| 50108 | JR Z,RunFrame_Add | Jump to RunFrame_Add if the zero flag is set. | ||
| 50110 | LD B,0 | No extra rows. | ||
| RunFrame_Add | 50112 | LD A,(49577) | The height of the ship. | |
| 50115 | ADD A,B | Add the extra rows. | ||
| 50116 | LD B,A | That is the collision height. | ||
| 50117 | CALL CheckTerrainCollision | Test the ship against the terrain. | ||
| 50120 | CALL CheckMapObjectCollisions | Test the ship against the map objects. | ||
| 50123 | LD HL,(51436) | The ship's horizontal speed. | ||
| 50126 | LD (51454),HL | Keep it for the end of the frame. | ||
| 50129 | LD HL,(51438) | The ship's vertical speed. | ||
| 50132 | LD (51456),HL | Keep it for the end of the frame. | ||
| 50135 | CALL SetShipSpeeds | Set the ship speeds from the scroll again. | ||
| 50138 | CALL MoveObject | Move the ship by those speeds. | ||
| RunFrame_Shots | 50141 | CALL UpdateShots | Call UpdateShots. | |
| 50144 | JP ScrollWorld | Jump to ScrollWorld. | ||
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This entry point is used by the routine at ScrollWorld.
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| RunFrame_Draw | 50147 | POP IY | Back to the pointer saved at the start of the frame. | |
| 50149 | LD A,(38571) | The crystal-delivery flag. | ||
| 50152 | AND A | A delivered stack draws nothing more this frame. | ||
| 50153 | RET NZ | |||
| 50154 | LD A,(36691) | The ship state. | ||
| 50157 | CP 11 | An explosion past ten draws nothing more. | ||
| 50159 | RET NC | |||
| 50160 | CALL StartCrystalObject | Call StartCrystalObject. | ||
| 50163 | LD A,(39524) | The frame counter. | ||
| 50166 | AND %00000001 | Bit 0 set means an odd frame. | ||
| 50168 | JR NZ,RunFrame_Ship | Jump to RunFrame_Ship if the zero flag is clear. | ||
| 50170 | CALL CheckItemDelivery | Call CheckItemDelivery. | ||
| 50173 | LD A,(51460) | The carried-item marker. | ||
| 50176 | AND A | Jump to RunFrame_Ship if A is not zero. | ||
| 50177 | JR NZ,RunFrame_Ship | |||
| 50179 | LD A,(36691) | The ship state. | ||
| 50182 | CP 10 | State ten skips the flame test. | ||
| 50184 | JR Z,RunFrame_Ship | |||
| 50186 | LD A,(48146) | A finished slope check skips the flames. | ||
| 50189 | AND A | Jump to RunFrame_Ship if A is not zero. | ||
| 50190 | JR NZ,RunFrame_Ship | |||
| 50192 | LD A,(23606) | The steering direction. | ||
| 50195 | AND A | Jump to DrawShipTop_Pause if A is zero. | ||
| 50196 | JP Z,DrawShipTop_Pause | |||
| 50199 | LD B,A | The direction being steered. | ||
| 50200 | LD A,(51453) | The ship's facing. | ||
| 50203 | XOR B | Flip the bits of A that are set in B. | ||
| 50204 | BIT 7,A | Jump to DrawShipTop_Pause if bit 7 of A is clear. | ||
| 50206 | JP Z,DrawShipTop_Pause | |||
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This entry point is used by the routine at UpdateCrystalStack.
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| RunFrame_Ship | 50209 | LD HL,0 | The draw scratch starts clear. | |
| 50212 | LD (23580),HL | The draw scratch starts at zero. | ||
| 50215 | LD A,(51459) | The ship's screen row. | ||
| 50218 | LD (41609),A | The row the sprites are drawn on. | ||
| 50221 | LD HL,1542 | A width and height of six. | ||
| 50224 | LD (23592),HL | The sprite size is six by six. | ||
| 50227 | LD IX,51429 | The ship. | ||
| 50231 | LD A,(36691) | The ship state. | ||
| 50234 | CP 10 | State ten skips the flame colour. | ||
| 50236 | JR Z,RunFrame_Erase | |||
| 50238 | LD C,(IX+24) | The ship's facing. | ||
| 50241 | LD A,(23606) | The direction being steered. | ||
| 50244 | AND A | Jump to RunFrame_Check if A is zero. | ||
| 50245 | JR Z,RunFrame_Check | |||
| 50247 | XOR C | Compare it with the facing byte. | ||
| 50248 | AND %10000000 | Only the facing bit. | ||
| 50250 | LD (51136),A | Note that the steering and the facing differ. | ||
| 50253 | JR Z,RunFrame_Check | Jump to RunFrame_Check if the zero flag is set. | ||
| 50255 | XOR A | Clear A. | ||
| 50256 | LD (23609),A | Clear the shot scratch. | ||
| RunFrame_Erase | 50259 | LD HL,(51458) | Where the ship was drawn. | |
| 50262 | LD (49027),HL | Keep that, so it can be erased. | ||
| 50265 | LD DE,(49578) | The ship graphic in the buffer. | ||
| 50269 | LD A,(49577) | The height of the ship. | ||
| 50272 | LD (23580),A | The height, kept for the draw. | ||
| 50275 | LD IY,42537 | The erase aligned row directly. | ||
| 50279 | CALL SelectMirroredErase | Call SelectMirroredErase. | ||
| 50282 | LD HL,(49027) | Fetch the word at 49027 into HL. | ||
| 50285 | CALL GetScreenAddress | Call GetScreenAddress. | ||
| 50288 | EXX | Switch to the alternate registers. | ||
| 50289 | LD A,(IX+31) | Read offset 31 of IX. | ||
| 50292 | AND A | Jump to RunFrame_Check if A is zero. | ||
| 50293 | JR Z,RunFrame_Check | |||
| 50295 | BIT 7,A | Jump to RunFrame_FitPart if bit 7 of A is clear. | ||
| 50297 | JR Z,RunFrame_FitPart | |||
| 50299 | CALL BuildCarriedItemGraphic | Call BuildCarriedItemGraphic. | ||
| 50302 | LD A,128 | A=128. | ||
| 50304 | LD (49786),A | A piece has been drawn. | ||
| 50307 | JR RunFrame_Facing | Jump to RunFrame_Facing. | ||
| RunFrame_FitPart | 50309 | LD B,A | B=A. | |
| 50310 | DEC A | Step A back. | ||
| 50311 | LD HL,62958 | The first part flag. | ||
| 50314 | CALL AddAToHL | Call AddAToHL. | ||
| 50317 | LD (HL),B | Write B where HL points. | ||
| 50318 | CALL DrawSpritesDirectly | Call DrawSpritesDirectly. | ||
| 50321 | CALL BuildShip | Call BuildShip. | ||
| 50324 | LD A,128 | A=128. | ||
| 50326 | LD (49786),A | A piece has been drawn. | ||
| 50329 | LD IX,51429 | The ship. | ||
| 50333 | LD HL,0 | HL=0. | ||
| 50336 | LD (23580),HL | No saved row count. | ||
| 50339 | LD HL,1542 | HL=1542. | ||
| 50342 | LD (23592),HL | The ship sprite is six bytes wide. | ||
| 50345 | JR RunFrame_Facing | Jump to RunFrame_Facing. | ||
| RunFrame_Check | 50347 | LD A,(IX+31) | Read offset 31 of IX. | |
| 50350 | AND A | Jump to RunFrame_Erase if A is not zero. | ||
| 50351 | JR NZ,RunFrame_Erase | |||
| RunFrame_Facing | 50353 | LD A,(23606) | The steering direction. | |
| 50356 | AND A | Jump to RunFrame_Explosion if A is zero. | ||
| 50357 | JR Z,RunFrame_Explosion | |||
| 50359 | LD (IX+24),A | Write A to offset 24 of IX. | ||
| RunFrame_Explosion | 50362 | LD A,(36691) | The ship state. | |
| 50365 | CP 10 | Jump to RunFrame_DrawShip if A is 10. | ||
| 50367 | JR Z,RunFrame_DrawShip | |||
| 50369 | LD A,(51459) | The row the ship was drawn on. | ||
| 50372 | LD (41610),A | The row the ship was drawn on. | ||
| 50375 | LD DE,(49578) | Fetch the word at ShipBufferAddress into DE. | ||
| 50379 | LD HL,(51458) | Fetch the word at 51458 into HL. | ||
| 50382 | LD (49027),HL | The position the ship was drawn at. | ||
| 50385 | CALL GetScreenAddress | Call GetScreenAddress. | ||
| 50388 | LD A,(49577) | The height of the ship. | ||
| 50391 | LD (23581),A | The height of the ship. | ||
| 50394 | LD IX,42616 | The draw aligned row directly. | ||
| 50398 | CALL SelectMirroredDraw | Call SelectMirroredDraw. | ||
| RunFrame_DrawShip | 50401 | CALL DrawSpritesDirectly | Call DrawSpritesDirectly. | |
| 50404 | CALL ColourShip | Call ColourShip. | ||
| 50407 | LD A,(36691) | The ship state. | ||
| 50410 | CP 10 | Return if A is 10 or more. | ||
| 50412 | RET NC | |||
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Continue on to DrawShipTop.
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| Prev: 49980 | Up: Map | Next: 50413 |