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A C64 Game - Step 59

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Endurion

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And yet another boss, this time a bit different than the previous two.

step59.png


;------------------------------------------------------------
;boss 3
;------------------------------------------------------------
!zone BehaviourBoss3
BehaviourBoss3
BOSS_MOVE_SPEED = 1
lda SPRITE_HITBACK,x
beq .NoHitBack
dec SPRITE_HITBACK,x

ldy SPRITE_HITBACK,x
lda BOSS_FLASH_TABLE,y
sta VIC_SPRITE_COLOR,x

cpy #0
bne .NoHitBack

;make vulnerable again
;lda SPRITE_STATE,x
;cmp #128
;bne .NoHitBack

lda #0
sta SPRITE_STATE,x

.NoHitBack
lda DELAYED_GENERIC_COUNTER
and #$01
beq +

rts

+
;y swing
inc SPRITE_MOVE_POS_Y,x
lda SPRITE_MOVE_POS_Y,x
and #15
sta SPRITE_MOVE_POS_Y,x

ldy SPRITE_MOVE_POS_Y,x
lda PATH_DY,y
beq .NoYMoveNeeded
sta PARAM1
and #$80
beq .MoveDown

;move up
lda PARAM1
and #$7f
sta PARAM1
.MoveUp
jsr ObjectMoveUp
dec PARAM1
bne .MoveUp

jmp BossFollowPlayerX

.MoveDown
jsr ObjectMoveDown
dec PARAM1
bne .MoveDown
.NoYMoveNeeded
jmp BossFollowPlayerX





The boss is supposed to move quite alike the first boss horizontally. Time to make that code piece a sub routine:




!zone BossFollowPlayerX
BOSS3_MOVE_SPEED = 2
.DoGhostMove
;move X times
ldy SPRITE_MOVE_POS,x
sty PARAM4
beq +

lda SPRITE_DIRECTION,x
beq .DoRight
.MoveLoopL
jsr ObjectMoveLeftBlocking
dec PARAM4
bne .MoveLoopL
+
rts

.DoRight
.MoveLoopR
jsr ObjectMoveRightBlocking
dec PARAM4
bne .MoveLoopR
rts
BossFollowPlayerX
inc SPRITE_ANIM_DELAY,x
lda SPRITE_ANIM_DELAY,x
cmp #10
beq .DoCheckMove
jmp .DoGhostMove
.DoCheckMove
lda #0
sta SPRITE_ANIM_DELAY,x

txa
and #$01
tay
lda SPRITE_ACTIVE,y
cmp #TYPE_PLAYER_DEAN
beq .FoundPlayer
cmp #TYPE_PLAYER_SAM
beq .FoundPlayer

;check other player
tya
eor #1
tay
lda SPRITE_ACTIVE,y
cmp #TYPE_PLAYER_DEAN
beq .FoundPlayer
cmp #TYPE_PLAYER_SAM
beq .FoundPlayer

;no player to hunt
rts

.FoundPlayer
;player index in y
lda SPRITE_CHAR_POS_X,y
cmp SPRITE_CHAR_POS_X,x
bpl .MoveRight

;move left
lda SPRITE_DIRECTION,x
bne .AlreadyLookingLeft
lda SPRITE_MOVE_POS,x
beq .TurnLNow
dec SPRITE_MOVE_POS,x
bne .CheckXDone

.TurnLNow
;turning now
lda #1
sta SPRITE_DIRECTION,x
lda #SPRITE_BOSS_ARM_L
sta SPRITE_POINTER_BASE,x
jmp .CheckXDone

.AlreadyLookingLeft
lda SPRITE_MOVE_POS,x
cmp #BOSS3_MOVE_SPEED
beq .CheckXDone
inc SPRITE_MOVE_POS,x
jmp .CheckXDone

.MoveRight
lda SPRITE_DIRECTION,x
beq .AlreadyLookingRight

lda SPRITE_MOVE_POS,x
beq .TurnRNow
dec SPRITE_MOVE_POS,x
bne .CheckXDone

;turning now
.TurnRNow
lda #0
sta SPRITE_DIRECTION,x
lda #SPRITE_BOSS_ARM_R
sta SPRITE_POINTER_BASE,x
jmp .CheckXDone

.AlreadyLookingRight
lda SPRITE_MOVE_POS,x
cmp #BOSS3_MOVE_SPEED
beq .CheckXDone
inc SPRITE_MOVE_POS,x
jmp .CheckXDone


.CheckXDone
rts




When the boss is hit he should be invulnerable for a short while, remember that we reserved the MSB in SPRITE_STATE for invincibility.


HitBehaviourBoss3
lda #8
sta SPRITE_HITBACK,x

;make invincible for a short while
lda SPRITE_STATE,x
ora #$80
sta SPRITE_STATE,x
rts


The rest boils down to the usual additions for a new object type.

Oh, and the new boss can only be hit if he shoots downwards! ;)

Have fun!


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