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.segment "CODE"
.scope Enemies
;; Maximum amount of enemies allowed on screen at the same time.
ENEMIES_POOL_CAPACITY = 3
;; The capacity of the bullets pool in bytes.
ENEMIES_POOL_CAPACITY_BYTES = ENEMIES_POOL_CAPACITY * 3
ENEMIES_INITIAL_X = $F0
;; TODO: 3 bytes a la bullets
zp_enemies_pool_base = $60 ; asan:reserve $09
zp_enemies_timer = $D0
zp_enemies_pool_size = $D1
.proc init
ldx #0
stx zp_enemies_timer
ldy #ENEMIES_POOL_CAPACITY
@enemies_init_loop:
lda #0
sta zp_enemies_pool_base, x
inx
stx Globals::zp_tmp0
jsr Prng::random_valid_y_coordinate
ldx Globals::zp_tmp0
sta zp_enemies_pool_base, x
inx
lda #ENEMIES_INITIAL_X
sta zp_enemies_pool_base, x
inx
dey
bne @enemies_init_loop
lda #ENEMIES_POOL_CAPACITY
sta zp_enemies_pool_size
rts
.endproc
.proc allocate_sprite_y
;; TODO
rts
.endproc
;; Definitions for all the enemy types. An enemy type is defined by four
;; bytes, containing the tile IDs for it. Some enemies only span 2 tiles,
;; and because of this they have $FF as filler bytes. Last but not least,
;; each enemy actually has two states in order to mock some inner movement.
;; This is also handled here and this is why an enemy spans a whooping 8
;; bytes of definition, which is fine because we have a lot of room to spare
;; in ROM space.
tiles:
;; Asteroid
.byte $26, $27, $36, $37
.byte $46, $47, $56, $57
;; Furry thingie
.byte $28, $29, $38, $39
.byte $48, $49, $58, $59
;; Bubble
.byte $24, $25, $34, $35
.byte $44, $45, $54, $55
;; Fighter jet 1
.byte $2A, $2B, $3A, $3B
.byte $2A, $2B, $3A, $3B
;; Fighter jet 2
.byte $31, $32, $FF, $FF
.byte $31, $32, $FF, $FF
;; UFO
.byte $40, $41, $FF, $FF
.byte $50, $51, $FF, $FF
;; Cross
.byte $2C, $2D, $3C, $3D
.byte $4C, $4D, $5C, $5D
;; Weirdo
.byte $2E, $2F, $3E, $3F
.byte $4E, $4F, $5E, $5F
.endscope
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