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Routines |
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Turns a speed into HorizontalSpeed and VerticalSpeed from the heading of the object. Headings zero and two move vertically, one and three horizontally. Headings two and three have a negative speed.
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Put the speed on the horizontal axis.
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| SetSpeedsFromHeading | CCC2 | LD H,$00 | Make the speed the horizontal speed, with no vertical speed. | |||||||
| CCC4 | LD L,A | |||||||||
| CCC5 | BIT 6,(IX+$06) | Jump to SetSpeedsFromHeading_Sign if the heading is horizontal. | ||||||||
| CCC9 | JR NZ,SetSpeedsFromHeading_Sign | |||||||||
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Put the speed on the vertical axis.
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| CCCB | LD H,A | Make the speed the vertical speed, with no horizontal speed. | ||||||||
| CCCC | LD L,$00 | |||||||||
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Make the speed negative for headings two and three.
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| SetSpeedsFromHeading_Sign | CCCE | BIT 7,(IX+$06) | Jump to SetSpeedsFromHeading_Store if the heading is not two or three. | |||||||
| CCD2 | JR Z,SetSpeedsFromHeading_Store | |||||||||
| CCD4 | LD A,L | Make the horizontal speed negative. | ||||||||
| CCD5 | NEG | |||||||||
| CCD7 | LD L,A | |||||||||
| CCD8 | LD A,H | Make the vertical speed negative. | ||||||||
| CCD9 | NEG | |||||||||
| CCDB | LD H,A | |||||||||
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Store the speeds.
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| SetSpeedsFromHeading_Store | CCDC | LD A,L | Set HorizontalSpeed. | |||||||
| CCDD | LD ($A214),A | |||||||||
| CCE0 | LD A,H | Set VerticalSpeed and return. | ||||||||
| CCE1 | LD ($A215),A | |||||||||
| CCE4 | RET | |||||||||
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View the equivalent code in;
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