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Routines |
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Used by the routines at 6E3C and 78AA. Returns with C and B holding the lower and upper x-coordinates of the range within which the target character can see or be seen. This routine is called with DE holding either (a) the coordinates of a teacher (to determine where kids must be in order to get lines), or (b) the coordinates of a kid (to determine where a teacher must be in order to give lines).
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6EA7 | LD A,E | A=x (character's x-coordinate) | ||||||||||
6EA8 | LD BC,$6000 | B=0x60, C=0x00 (maximum and minimum bounds) | ||||||||||
6EAB | SUB $0A | Is the character's x-coordinate < 10? | ||||||||||
6EAD | JR C,$6EC4 | Jump if so | ||||||||||
6EAF | LD C,A | C=x-10 | ||||||||||
6EB0 | LD A,D | A=floor nearest to the character | ||||||||||
6EB1 | CP $A9 | Is the character nearest the bottom floor? | ||||||||||
6EB3 | JR Z,$6EC4 | Jump if so | ||||||||||
6EB5 | CP $A2 | Set the zero flag if the character is nearest the middle floor | ||||||||||
6EB7 | LD A,$26 | This is the x-coordinate of the Exam Room wall | ||||||||||
6EB9 | JR Z,$6EBD | Jump if the character is nearest the middle floor | ||||||||||
6EBB | LD A,$39 | This is the x-coordinate of the Map Room wall | ||||||||||
6EBD | CP C | Is the character more than 10 paces to the right of a wall? | ||||||||||
6EBE | JR C,$6EC4 | Jump if so | ||||||||||
6EC0 | CP E | Is the character to the left of a wall? | ||||||||||
6EC1 | JR NC,$6EC4 | Jump if so | ||||||||||
6EC3 | LD C,A | C=x-coordinate of the wall that the character is within 10 paces to the right of | ||||||||||
Now C holds the lower x-coordinate of the visibility range. Time to calculate the upper x-coordinate.
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6EC4 | LD A,E | A=x (character's x-coordinate) | ||||||||||
6EC5 | ADD A,$0A | A=x+10 | ||||||||||
6EC7 | CP B | Is the character within 10 paces of the far right wall? | ||||||||||
6EC8 | RET NC | Return if so | ||||||||||
6EC9 | LD B,A | B=x+10 | ||||||||||
6ECA | LD A,D | A=floor nearest to the character | ||||||||||
6ECB | CP $A9 | Is the character nearest the bottom floor? | ||||||||||
6ECD | RET Z | Return if so | ||||||||||
6ECE | CP $A2 | Set the zero flag if the character is nearest the middle floor | ||||||||||
6ED0 | LD A,$25 | This is the x-coordinate of the White Room wall | ||||||||||
6ED2 | JR Z,$6ED6 | Jump if the character is nearest the middle floor | ||||||||||
6ED4 | LD A,$38 | This is the x-coordinate of the Reading Room wall | ||||||||||
6ED6 | CP B | Is the character more than 10 paces to the left of a wall? | ||||||||||
6ED7 | RET NC | Return if so | ||||||||||
6ED8 | CP E | Is the character to the right of a wall? | ||||||||||
6ED9 | RET C | Return if so | ||||||||||
6EDA | LD B,A | B=x-coordinate of the wall | ||||||||||
6EDB | RET |
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