Gunfright: Routine at A8D5

Type 17: a tumbleweed rolling about next to the sheriff. It follows one of two routes, stepping through the route one byte at a time; the high nibble of each byte is the vertical speed and the low nibble the horizontal speed, both signed. Bits 6 and 7 of byte 05 mirror the route, and they change every time a route ends, so the tumbleweed wanders in a different way each time. It spins by flipping its sprite every frame, and it hurts the sheriff if they touch. It goes away when the sheriff is two cells away.

Type 17: a tumbleweed rolling about next to the sheriff. It follows one of two routes, stepping through the route one byte at a time; the high nibble of each byte is the vertical speed and the low nibble the horizontal speed, both signed. Bits 6 and 7 of byte 05 mirror the route, and they change every time a route ends, so the tumbleweed wanders in a different way each time. It spins by flipping its sprite every frame, and it hurts the sheriff if they touch. It goes away when the sheriff is two cells away.
Disappear if the sheriff is more than two cells away.
HandleTumbleweed	A8D5	LD C,$02	Set the distance to two cells.
	A8D7	CALL CheckDistance	Check how close the sheriff is.
	A8DA	JP NC,HandleBody_Remove	Remove the tumbleweed if the sheriff has moved away.
Fetch the next step of the route.
	A8DD	LD A,(IX+$0A)	Fetch the number of the route, zero or one.
	A8E0	LD BC,$A94B	Point BC at TumbleweedRoutes.
	A8E3	CALL GetTableEntry	Point HL at the start of the route.
	A8E6	LD A,(IX+$0B)	Fetch the position in the route.
	A8E9	INC (IX+$0B)	Move on to the next step.
	A8EC	CALL AddAToHL	Point HL at the step.
	A8EF	LD A,(HL)	Fetch the step.
	A8F0	CP $80	Jump to HandleTumbleweed_RouteEnd if this is the end of the route.
	A8F2	JR Z,HandleTumbleweed_RouteEnd
Work out the vertical speed from the high nibble.
	A8F4	SRA A	Shift the high nibble into the bottom of the byte, keeping the sign.
	A8F6	SRA A
	A8F8	SRA A
	A8FA	SRA A
	A8FC	BIT 6,(IX+$05)	Jump to HandleTumbleweed_DoubleVertical unless the route is mirrored vertically.
	A900	JR Z,HandleTumbleweed_DoubleVertical
	A902	NEG	Negate the speed to mirror the route.
HandleTumbleweed_DoubleVertical	A904	SLA A	Double the speed.
	A906	LD ($A215),A	Store it as the vertical speed.
Work out the horizontal speed from the low nibble.
	A909	LD A,(HL)	Fetch the step again.
	A90A	LD C,A	Keep the tumbleweed step in C.
	A90B	AND %00001111	Keep the low nibble.
	A90D	BIT 3,C	Jump to HandleTumbleweed_TestHorizontal unless the nibble is negative.
	A90F	JR Z,HandleTumbleweed_TestHorizontal
	A911	OR %11110000	Extend the sign of the nibble into the top half.
HandleTumbleweed_TestHorizontal	A913	BIT 7,(IX+$05)	Jump to HandleTumbleweed_DoubleHorizontal unless the route is mirrored horizontally.
	A917	JR Z,HandleTumbleweed_DoubleHorizontal
	A919	NEG	Negate the speed to mirror the route.
HandleTumbleweed_DoubleHorizontal	A91B	SLA A	Double the speed.
	A91D	LD ($A214),A	Store it as the horizontal speed.
Move the tumbleweed.
	A920	CALL CheckWallsEachWay	Set the direction the tumbleweed is facing from its speed.
	A923	CALL MoveObject	Move the tumbleweed.
	A926	LD A,(IX+$07)	Fetch the flags of the object.
	A929	XOR %01000000	Flip the sprite horizontally.
	A92B	LD (IX+$07),A	Store the flags.
	A92E	CALL CheckSheriffTouch	Check whether the tumbleweed is touching the sheriff.
	A931	JP C,KillSheriff	Hurt the sheriff if it is.
	A934	RET	Return.
The route has ended, so choose the next one.
HandleTumbleweed_RouteEnd	A935	LD A,($A218)	Fetch a random number.
	A938	AND %00000001	Keep bit 0.
	A93A	LD (IX+$0A),A	Choose the route with it.
	A93D	LD (IX+$0B),$00	Write 00 to byte 0B to go back to the first step.
	A941	LD A,(IX+$05)	Fetch the mirror flags.
	A944	ADD A,$40	Add 40 to change how the route is mirrored.
	A946	LD (IX+$05),A	Store the flags.
	A949	JR HandleTumbleweed	Start again with the new route.