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Routines |
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Used by the routine at start.
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| dec_timer_move_aliens | 24795 | LD A,(_ALIENS_SPEED_CONTROL) | Pick up speed control, decrement it, if it's not zero it's not yet time to move the aliens. | |
| 24798 | DEC A | |||
| 24799 | LD (_ALIENS_SPEED_CONTROL),A | |||
| 24802 | RET NZ | |||
| 24803 | CALL move_aliens | Move aliens, drop through | ||
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Aliens have been moved, now recalculate speed control based on how many are left. This puts a number in _ALIENS_SPEED_CONTROL. The algorihm is SPEED_CONTROL = (NUM_LEFT/4 + NUM_LEFT/8) + 4
This entry point is used by the routine at start.
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| set_alien_speed | 24806 | LD A,(_NUM_ALIENS_REMAINING) | How many are left? | |
| 24809 | SRL A | /2 | ||
| 24811 | SRL A | /4 | ||
| 24813 | LD B,A | Div by 4 in B | ||
| 24814 | SRL A | /8 | ||
| 24816 | ADD A,B | div8 + div4 | ||
| 24817 | ADD A,4 | +4 | ||
| 24819 | LD (_ALIENS_SPEED_CONTROL),A | Result | ||
| 24822 | RET | |||
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