Krakout: Pick a new wander heading on a timer

C8C2: Pick a new wander heading on a timer

Drives the wander of an inhabitant or the ball gem: after a random 33–64 frames it picks a new heading.

Input
A	heading restriction: 0 for any heading, 1 for diagonal only, 2 for straight only, 3 for right or left only, 4 or more for up or down only
IY	the object's logic record (obj2_record)

The restriction in A limits the new heading. It allows any of the eight headings, only the four diagonals or only the four straight ones. It can also allow only right or left, or only up or down.

pick_wander_heading

C8C2

LD B,A

Save the heading restriction in B.

C8C3

LD A,(IY+$07)

Wander timer not yet expired? Hold the heading.

C8C6

OR A

C8C7

JR Z,wander_new_heading

C8C9

DEC (IY+$07)

Count the timer down and return.

C8CC

RET

wander_new_heading

C8CD

CALL next_random

Timer expired: reload it with a random wander time.

C8D0

AND $1F

C8D2

ADD A,$20

C8D4

LD (IY+$07),A

C8D7

LD A,B

Any random heading

C8D8

OR A

C8D9

JR NZ,wander_odd

C8DB

CALL next_random

C8DE

AND $07

C8E0

LD (IY+$00),A

C8E3

RET

wander_odd

C8E4

CP $01

A random diagonal heading

C8E6

JR NZ,wander_even

C8E8

CALL next_random

C8EB

AND $07

C8ED

OR $01

C8EF

LD (IY+$00),A

C8F2

RET

wander_even

C8F3

CP $02

A random straight heading

C8F5

JR NZ,wander_horizontal

C8F7

CALL next_random

C8FA

AND $06

C8FC

LD (IY+$00),A

C8FF

RET

wander_horizontal

C900

CP $03

A horizontal heading, rightward or leftward

C902

JR NZ,wander_vertical

C904

CALL next_random

C907

AND $01

C909

ADD A,A

C90A

ADD A,A

C90B

ADD A,$02

C90D

LD (IY+$00),A

C910

RET

wander_vertical

C911

CALL next_random

A vertical heading, up or down

C914

AND $01

C916

ADD A,A

C917

ADD A,A

C918

LD (IY+$00),A

C91B

RET

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Routines