Ant Attack: Routine at 8800

8800: Move an object one frame: fall, climb, jump, walk

Used by the routine at MOVE_OR_RESPAWN.

The physics for everything. Nothing is solid but the map, and ants put themselves in the map (TOGGLE_MAP_BIT), so walking into an ant is walking into a wall -- and an ant arriving in someone's cell is a bite.

Input
IX	The object

MOVE_OBJECT

8800

LD L,(IX+$00)

Where it is.

8803

LD H,(IX+$01)

8806

LD C,(IX+$02)

8809

LD D,H

Anything to stand on? If not, fall.

880A

LD E,L

880B

LD A,C

880C

DEC A

880D

CALL TEST_BELOW

8810

JP NC,FALL

This entry point is used by the routine at FALL.

MOVE_OBJECT_0

8813

LD D,H

Something in this very cell: bitten, and pushed up.

8814

LD E,L

8815

LD A,C

8816

CALL TEST_MAP_BIT

8819

JP C,BITTEN

881C

LD A,(IX+$06)

Stunned: count it down.

881F

AND A

8820

JP NZ,STUNNED

8823

LD A,(IX+$05)

Just landed from a fall.

8826

CP $02

8828

JP NC,LANDED

882B

XOR A

Standing.

882C

LD (IX+$05),A

882F

BIT 1,(IX+$07)

Jump.

8833

JP NZ,RISE

This entry point is used by the routines at FALL and RISE.

MOVE_OBJECT_1

8836

BIT 2,(IX+$07)

Walk forward, if moving...

883A

JP Z,MOVE_OBJECT_2

883D

LD A,(IX+$04)

...a cell the way it faces...

8840

CALL STEP

8843

LD D,H

8844

LD E,L

8845

LD A,C

8846

CALL TEST_MAP_BIT

8849

JP C,STEP_UP

...unless the way is blocked.

884C

LD (IX+$00),L

A step.

884F

LD (IX+$01),H

8852

LD (IX+$0F),$01

MOVE_OBJECT_2

8856

RET