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Routines |
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Used by the routine at FireWeapons.
Used when the extra key is pressed. If there is no special shot at B832 and the ship has part 07 and is moving slowly in both directions, launches one. If there is one already, goes to DetonateSpecialShot.
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| CheckSpecialShot | B833 | LD A,($B832) | The special-shot flag. | |
| B836 | AND A | Jump to DetonateSpecialShot if A is not zero. | ||
| B837 | JR NZ,DetonateSpecialShot | |||
| B839 | LD A,($5C37) | The controls. | ||
| B83C | BIT 5,A | Return if bit 5 of A is clear. | ||
| B83E | RET Z | |||
| B83F | LD A,($F5F4) | The seventh part, which makes a special shot. | ||
| B842 | AND A | Return if A is zero. | ||
| B843 | RET Z | |||
| B844 | LD HL,($C8FE) | Fetch the word at C8FE into HL. | ||
| B847 | LD A,H | A=H. | ||
| B848 | LD H,L | H=L. | ||
| B849 | LD L,A | L=A. | ||
| B84A | CALL ZeroSmallSpeed | Call ZeroSmallSpeed. | ||
| B84D | LD A,H | A=H. | ||
| B84E | OR L | Set the bits of A that are set in L. | ||
| B84F | RET NZ | Return if the zero flag is clear. | ||
| B850 | LD HL,($C900) | Fetch the word at C900 into HL. | ||
| B853 | LD A,H | A=H. | ||
| B854 | LD H,L | H=L. | ||
| B855 | LD L,A | L=A. | ||
| B856 | CALL ZeroSmallSpeed | Call ZeroSmallSpeed. | ||
| B859 | LD A,H | A=H. | ||
| B85A | OR L | Set the bits of A that are set in L. | ||
| B85B | RET NZ | Return if the zero flag is clear. | ||
| B85C | LD A,($B730) | The weapon toggle. | ||
| B85F | XOR %00000100 | Flip the bits of A that are set in 04. | ||
| B861 | LD ($B730),A | Update the weapon toggle. | ||
| B864 | CALL LaunchShot | Call LaunchShot. | ||
| B867 | LD A,($B730) | The weapon toggle. | ||
| B86A | AND %00000001 | Keep the bits of A that are set in 01. | ||
| B86C | LD ($B730),A | Update the weapon toggle. | ||
| B86F | RET | Return. | ||
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This entry point is used by the routine at CheckObjectHitByShot.
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| FindShot | B870 | LD IY,$B37A | The shot slots. | |
| B874 | LD DE,$0018 | DE=18. | ||
| B877 | LD B,$03 | B=03. | ||
| CheckSpecialShot_Loop | B879 | BIT 7,(IY+$16) | Jump to CheckSpecialShot_Next if bit 7 of offset 16 of IY is set. | |
| B87D | JR NZ,CheckSpecialShot_Next | |||
| B87F | BIT 7,(IY+$15) | Return if bit 7 of offset 15 of IY is set. | ||
| B883 | RET NZ | |||
| CheckSpecialShot_Next | B884 | ADD IY,DE | IY gains DE. | |
| B886 | DJNZ CheckSpecialShot_Loop | Decrease B and jump to CheckSpecialShot_Loop until none remain. | ||
| B888 | RET | Return. | ||
| DetonateSpecialShot | B889 | LD A,($5C37) | The controls. | |
| B88C | BIT 5,A | Return if bit 5 of A is set. | ||
| B88E | RET NZ | |||
| B88F | CALL FindShot | Call FindShot. | ||
| B892 | SET 7,(IY+$10) | Set bit 7 of offset 10 of IY. | ||
| B896 | RET | Return. | ||
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