Atic Atac: Routine at 9ABA

Used by the routines at DRAW_UPSIDE_DOWN, BLIT_SPRITE_FLIPPED, DRAW_FLIP_DIAGONAL, DRAW_TURNED_LEFT, COLOURS_UPSIDE_DOWN, COLOURS_HALF_TURN, COLOURS_FLIP_DIAGONAL and COLOURS_TURNED_LEFT.

Multiplies the width by the height less one and adds it to the data pointer, so drawing can start from the far end. Called by every drawing routine whose mode number has bit 2 set -- which is how the eight modes divide: the low two bits choose the horizontal treatment and bit 2 turns the sprite over.

Checking all sixteen routines in the two tables bears that out exactly. Modes 0 to 3 leave the pointer where it is; modes 4 to 7 all begin by calling this.

Used by the routines at DRAW_UPSIDE_DOWN, BLIT_SPRITE_FLIPPED, DRAW_FLIP_DIAGONAL, DRAW_TURNED_LEFT, COLOURS_UPSIDE_DOWN, COLOURS_HALF_TURN, COLOURS_FLIP_DIAGONAL and COLOURS_TURNED_LEFT. Multiplies the width by the height less one and adds it to the data pointer, so drawing can start from the far end. Called by every drawing routine whose mode number has bit 2 set -- which is how the eight modes divide: the low two bits choose the horizontal treatment and bit 2 turns the sprite over. Checking all sixteen routines in the two tables bears that out exactly. Modes 0 to 3 leave the pointer where it is; modes 4 to 7 all begin by calling this.
START_AT_LAST_ROW	9ABA	PUSH HL
	9ABB	PUSH DE
	9ABC	LD A,B
	9ABD	LD E,C
	9ABE	DEC E
	9ABF	LD D,$00
	9AC1	PUSH BC
	9AC2	CALL MULTIPLY
	9AC5	POP BC
	9AC6	POP DE
	9AC7	ADD HL,DE
	9AC8	EX DE,HL
	9AC9	POP HL
	9ACA	RET