Robotron: 2084: Routine at CD34

CD34: Clear Colour Bar Column

Used by the routines at Handle_Homing_Enemy, Process_Entity_Record_Fast, Kill_Tracked_Enemy_Entity, Process_Cluster_Entity, Kill_Wall_Bouncing_Enemy and Process_Final_Phase_Enemy_Entity. Clears a seven-column, six-pixel-row strip from the screen pixel area at the column position held in Colour_Bar_Column, then jumps to PrintPlayerScore to redraw the column.
Clear_Colour_Bar_Column	CD34	LD B,$06	Prepare to clear six pixel rows of the colour bar column.
	CD36	LD H,$42	Prepare to clear six pixel rows of the colour bar column.
For each row, point to the target column and zero seven pixel cells.
Clear_Colour_Bar_Column_Row	CD38	LD A,($C420)	Point to the colour bar column in the current pixel row.
	CD3B	LD L,A	Point to the colour bar column in the current pixel row.
	CD3C	XOR A	Zero seven pixel cells at the column position.
	CD3D	LD (HL),A
	CD3E	INC HL
	CD3F	LD (HL),A
	CD40	INC HL
	CD41	LD (HL),A
	CD42	INC HL
	CD43	LD (HL),A
	CD44	INC HL
	CD45	LD (HL),A
	CD46	INC HL
	CD47	LD (HL),A
	CD48	INC HL
	CD49	LD (HL),A
	CD4A	INC H	Advance to the next pixel row and repeat until all six are cleared.
	CD4B	DJNZ Clear_Colour_Bar_Column_Row
	CD4D	JP PrintPlayerScore	Jump to PrintPlayerScore to redraw the score display column.