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Routines |
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Used by the routine at RunGame.
Counts the light years down, prints the four digits in the counter box, inverts the last of them and copies the counter to the screen. When all of the digits and their animation steps are zero the game is over. The light years go down by one every eight frames.
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Print the four digits into the buffer.
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| UpdateLightYears | 44390 | CALL DecrementLightYears | Call DecrementLightYears. | |
| 44393 | CALL RollCounterDigits | Call RollCounterDigits. | ||
| 44396 | LD HL,54522 | Point HL at ScreenBuffer_LightYears. | ||
| 44399 | LD DE,23350 | Point DE at LightYearsRemaining. | ||
| 44402 | LD B,4 | Set a counter of four digits. | ||
| 44404 | PUSH HL | Stash the buffer address on the stack. | ||
| 44405 | LD HL,25352 | Point HL at Font. | ||
| 44408 | LD (23335),HL | Set FontPointer. | ||
| 44411 | POP HL | Restore the buffer address from the stack. | ||
| UpdateLightYears_PrintDigit | 44412 | LD A,(DE) | Fetch the digit and its animation step. | |
| 44413 | INC DE | Move on to the next digit. | ||
| 44414 | CALL PrintCounterDigit | Call PrintCounterDigit. | ||
| 44417 | DJNZ UpdateLightYears_PrintDigit | Jump to UpdateLightYears_PrintDigit until all four digits have been printed. | ||
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Invert the last digit and copy the counter to the screen.
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| 44419 | LD HL,54301 | Point HL at ScreenBuffer_LightYearsLastDigit. | ||
| 44422 | LD B,8 | Set a counter of eight pixel rows. | ||
| 44424 | LD DE,32 | Set DE to 0032. | ||
| UpdateLightYears_InvertRow | 44427 | LD A,(HL) | Fetch a row of the last digit. | |
| 44428 | CPL | Invert it. | ||
| 44429 | LD (HL),A | Store it. | ||
| 44430 | ADD HL,DE | Move up to the next row. | ||
| 44431 | DJNZ UpdateLightYears_InvertRow | Jump to UpdateLightYears_InvertRow until all eight rows have been inverted. | ||
| 44433 | LD BC,4304 | Set the pixel position to 208, 16. | ||
| 44436 | CALL CalculateScreenAddress | Call CalculateScreenAddress. | ||
| 44439 | CALL CalculateBufferAddress | Call CalculateBufferAddress. | ||
| 44442 | LD L,C | Copy the buffer address to HL. | ||
| 44443 | LD H,B | |||
| 44444 | LD BC,2052 | Set the size to eight rows of four bytes. | ||
| 44447 | CALL CopyBlockToScreen | Call CopyBlockToScreen. | ||
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End the game if every digit is zero.
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| 44450 | LD HL,23350 | Point HL at LightYearsRemaining. | ||
| 44453 | LD B,4 | Set a counter of four digits. | ||
| 44455 | XOR A | Set A to 0. | ||
| UpdateLightYears_TestDigit | 44456 | OR (HL) | Combine the digit with the others. | |
| 44457 | INC HL | Move on to the next digit. | ||
| 44458 | DJNZ UpdateLightYears_TestDigit | Jump to UpdateLightYears_TestDigit until all four have been combined. | ||
| 44460 | JP Z,GameOver | Jump to GameOver if all of the digits are zero. | ||
| 44463 | RET | Return. | ||
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