A C64 Game - Step 77

And another boss. This one is different, as it spawns bats to the left and right. And is only vulnerable during that part ;)



The boss routine is a bit bigger this time. The attacking bat code is already there, so nothing to add on that part.
As behaviours got increasingly complex I started to write the state values on top of the routines. Remember, any states with MSB set (>=128) mark the object as invincible.

;------------------------------------------------------------
;boss #5
;state 128 = find target Y
;state 129 = move towards target Y
;state 0 = attack
;state 130 = cool off
;------------------------------------------------------------
!zone BehaviourBoss6
BehaviourBoss6
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
          lda #1
          sta VIC_SPRITE_COLOR,x

          ;keep invulnerable
.NoHitBack
          lda DELAYED_GENERIC_COUNTER
          and #$03
          bne .NoAnimUpdate

.NoAnimUpdate
          lda SPRITE_STATE,x
          beq .Attack
          cmp #128
          bne +
          jmp .FindTargetY

+
          cmp #129
          beq .MoveTowardsTarget
          cmp #130
          beq .CoolOff

          lda #0
          sta SPRITE_STATE,x
          rts

.CoolOff
          inc SPRITE_MODE_POS,x
          lda SPRITE_MODE_POS,x
          cmp #30
          bne +

          lda #128
          sta SPRITE_STATE,x

+
          rts

.Attack
          inc SPRITE_MOVE_POS,x
          lda SPRITE_MOVE_POS,x
          and #$1f
          cmp #$1f
          beq +
          rts

+
          ;free bats
          inc SPRITE_MODE_POS,x
          lda SPRITE_MODE_POS,x
          cmp #5
          bne +

          lda #130
          sta SPRITE_STATE,x
          lda #0
          sta SPRITE_MODE_POS,x
          rts

+
          lda SPRITE_CHAR_POS_X,x
          sta PARAM1
          lda SPRITE_CHAR_POS_Y,x
          sta PARAM2
          inc PARAM2
          stx PARAM10
          jsr FindEmptySpriteSlot
          beq ++

          lda #TYPE_BAT_ATTACKING
          sta PARAM3
          jsr SpawnObject
          lda #0
          sta SPRITE_DIRECTION,x
          jsr FindEmptySpriteSlot
          beq ++
          jsr SpawnObject
          lda #1
          sta SPRITE_DIRECTION,x

++
          ldx PARAM10
          rts

.MoveTowardsTarget
          ;player index in y
          lda SPRITE_VALUE,x
          cmp SPRITE_CHAR_POS_Y,x
          bne +

          ;arrived at target Y
          lda #0
          sta SPRITE_MODE_POS,x
          sta SPRITE_STATE,x
          rts

+
          bpl .MoveDown

          ;move up?
          lda SPRITE_DIRECTION_Y,x
          bne .AlreadyLookingUp
          lda SPRITE_MOVE_POS_Y,x
          beq .TurnUNow
          dec SPRITE_MOVE_POS_Y,x
          bne .DoGhostMove

.TurnUNow
          ;turning now
          lda #1
          sta SPRITE_DIRECTION_Y,x
          jmp .DoGhostMove

.AlreadyLookingUp
          lda SPRITE_MOVE_POS_Y,x
          cmp #BOSS_MOVE_SPEED
          beq .DoGhostMove
          inc SPRITE_MOVE_POS_Y,x
          jmp .DoGhostMove

.MoveDown
          lda SPRITE_DIRECTION_Y,x
          beq .AlreadyLookingDown

          lda SPRITE_MOVE_POS_Y,x
          beq .TurnDNow
          dec SPRITE_MOVE_POS_Y,x
          bne .DoGhostMove

          ;turning now
.TurnDNow
          lda #0
          sta SPRITE_DIRECTION_Y,x
          jmp .DoGhostMove

.AlreadyLookingDown
          lda SPRITE_MOVE_POS_Y,x
          cmp #BOSS_MOVE_SPEED
          beq .DoGhostMove
          inc SPRITE_MOVE_POS_Y,x
          jmp .DoGhostMove

.DoGhostMove
          ;move X times
          ldy SPRITE_MOVE_POS_Y,x
          sty PARAM4
          beq .MoveDone

          lda SPRITE_DIRECTION_Y,x
          beq .DoDown

.MoveLoopU
          jsr ObjectMoveUpBlocking
          dec PARAM4
          bne .MoveLoopU
          jmp .MoveDone

.DoDown
.MoveLoopD
          jsr ObjectMoveDownBlockingNoPlatform
          dec PARAM4
          bne .MoveLoopD

.MoveDone
          rts

.FindTargetY
          lda #4
          sta PARAM5
          lda #18
          sta PARAM6
          jsr GenerateRangedRandom
          sta SPRITE_VALUE,x
          inc SPRITE_STATE,x
          rts

Have fun!


step77.zip