jetpac: Routine at 6d9c

6d9c: Update the meteor.

Input
IX	Alien object.

6d9c

call $72ef

Update Actor position direction

6d9f

ld hl,$5dcb

Increment alien number

6da2

inc (hl)

Update the alien X position.

6da3

ld a,(ix+$01)

A=X position

6da6

bit 6,(ix+$04)

Check moving left/right bit

6daa

jr nz,$6de4

If moving left, subtract 2 from direction (via jump)

6dac

add a,(ix+$05)

otherwise, we add alien X speed to value

6daf

ld (ix+$01),a

Set new X position +/- 2

Update the alien Y position.

6db2

ld a,(ix+$02)

Add Y speed to current Y position

6db5

add a,(ix+$06)

6db8

ld (ix+$02),a

6dbb

call $7232

Update actor X position (using temp direction)

6dbe

call $7197

Colourize the sprite

6dc1

call $75e8

Platform collision (returns E)

6dc4

bit 2,e

Kill alien it collided with a platform

6dc6

jr nz,$6ddd

6dc8

call $6e1b

Fire laser beam (returns C)

6dcb

ld a,c

Kill alien if it is dead

6dcc

and a

6dcd

jr nz,$6dd7

6dcf

call $6de9

Alien collision check (returns E)

6dd2

dec e

Alien killed by collision if E is zero. Player gets no points!

6dd3

jp z,$6456

6dd6

ret

Add score for Meteor kill.

6dd7

ld bc,$0025

25 points (decimal value)

6dda

call $70c2

Add points to score

Kill meteor - reset state, and play explosion SFX #1.

6ddd

call $685d

Update actor state

6de0

xor a

A should be 0 for the Alien SFX

6de1

jp $67fd

Plays explosion SFX for an Alien

Subtract 2 from horizontal direction.

6de4

sub (ix+$05)

Subtract X speed

6de7

jr $6daf