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Routines |
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Used by the routine at UpdateShipSpeeds.
Adds the acceleration in DE to the horizontal speed of the ship, limits it, and sets it to zero if the ship has turned round. Carries on at UpdateHorizontalScrollSpeed to work out the horizontal scroll speed.
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| UpdateHorizontalSpeed | C7FC | LD H,(IX+$19) | Read offset 19 of IX into H. | |||||||
| C7FF | LD L,(IX+$1A) | Read offset 1A of IX into L. | ||||||||
| C802 | EX DE,HL | Swap DE and HL. | ||||||||
| C803 | ADD HL,DE | HL gains DE. | ||||||||
| C804 | CALL LimitHorizontalSpeed | Call LimitHorizontalSpeed. | ||||||||
| C807 | LD A,($5C36) | The steering direction. | ||||||||
| C80A | AND A | Jump to UpdateHorizontalSpeed_Store if A is not zero. | ||||||||
| C80B | JR NZ,UpdateHorizontalSpeed_Store | |||||||||
| C80D | LD A,H | A=H. | ||||||||
| C80E | XOR D | Flip the bits of A that are set in D. | ||||||||
| C80F | AND %10000000 | Keep the bits of A that are set in 80. | ||||||||
| C811 | JR Z,UpdateHorizontalSpeed_Store | Jump to UpdateHorizontalSpeed_Store if the zero flag is set. | ||||||||
| C813 | LD HL,$0000 | HL=00. | ||||||||
| C816 | LD ($C7FA),HL | Update the horizontal scroll fraction. | ||||||||
| UpdateHorizontalSpeed_Store | C819 | LD (IX+$19),H | Write H to offset 19 of IX. | |||||||
| C81C | LD (IX+$1A),L | Write L to offset 1A of IX. | ||||||||
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Continue on to UpdateHorizontalScrollSpeed.
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