Sabre Wulf: Routine at 47964

47964: Clear Play Area

Used by the routines at GameComplete, 41479, HandlerPoems, GameOver_1UP, 45359, 45524, 45573 and HandlerGameMenu.
This routine clears the top third of the screen, but only from below the banner. This is left untouched.
ClearPlayArea	47964	LD HL,16448	HL=16448(screen buffer).
Here D contains the value to be written (0) and E holds the number of rows of pixels to act on (the full height of a character block).
	47967	LD DE,8	DE=0008.
B holds the number of columns (i.e. 32 == full width of the screen), and C is a counter for how many rows to clear (i.e. the top third would usually be 8 rows, but the banner takes up two - hence this initialises to 6).
	47970	LD BC,8198	BC=8198.
ClearPlayArea_ClearLine	47973	PUSH BC	Stash BC and HL on the stack.
	47974	PUSH HL	Stash BC and HL on the stack.
ClearPlayArea_ClearLine_Start	47975	PUSH BC	Stash BC on the stack.
ClearPlayArea_ClearLine_Loop	47976	LD (HL),D	Write 0 (D) to the screen (HL).
	47977	INC L	Move "right" onto the next column.
	47978	DJNZ ClearPlayArea_ClearLine_Loop	Decrease the width counter by one and loop back to ClearPlayArea_ClearLine_Loop until counter is zero.
Resets the width counter ready for the next loop.
	47980	POP BC	Restore BC from the stack.
	47981	DEC C	Decrease the number of rows counter by one.
	47982	JR NZ,ClearPlayArea_ClearLine_Start	Jump back to ClearPlayArea_ClearLine_Start unless C is zero.
Resets the screen buffer to where the clearing started for this loop, then moves down one character block.
	47984	POP HL	Restore HL from the stack.
	47985	INC H	Increments H by one.
	47986	POP BC	Restore BC from the stack.
	47987	DEC E	Decrease the pixel row counter by one.
	47988	JR NZ,ClearPlayArea_ClearLine	Jump back to ClearPlayArea_ClearLine unless E is zero.
Clears the other two thirds of the screen, so now the screen only contains the banner.
	47990	LD HL,18432	HL=18432(screen buffer).
	47993	JP ResetScreen_0	Jump to ResetScreen_0.