Through the Trap Door: Routine at 53782

53782: Set each value in primary display buffer within play area to zero

Used by the routine at 34438.
53782	LD HL,(34279)	Load HL with start address of primary display buffer
53785	LD BC,704	Set BC to 704, as there are 704 entries in a display buffer
53788	LD DE,3	Load DE with 3 as each entry in the display buffer is three bytes wide
53791	LD A,(HL)	Read first byte in display buffer...
53792	INC A	...and add one
53793	JP Z,53806	If value is now zero (i.e. was previously 255 and therefore outside normal play area), then skip ahead to 53806
53796	XOR A	Set all values in current entry to zero...
53797	LD (HL),A	...
53798	INC HL	...
53799	LD (HL),A	...
53800	INC HL	...
53801	LD (HL),A	...
53802	INC HL	...
53803	JP 53807	Skip ahead to 53807
53806	ADD HL,DE	Advance current position in display buffer to next entry
53807	DEC BC	Decrease remaining number of entries to process
53808	LD A,B	If remaining number of entries is not zero...
53809	OR C	...
53810	JP NZ,53791	...then loop back to 53791
53813	RET	Return