update_hero_x.s

; vim: set syntax=asm_ca65:

.include "constants.inc"

.segment "ZEROPAGE"

.import hero_x_coord
.import controller_1_input

.segment "CODE"

.proc update_hero_x
  PHP
  PHA
  TXA
  PHA
  TYA
  PHA

  LDA controller_1_input
  AND #BTN_LEFT
  BEQ check_right
  DEC hero_x_coord

check_right:
  LDA controller_1_input
  AND #BTN_RIGHT
  BEQ done_checking
  INC hero_x_coord

done_checking:
  LDA hero_x_coord

  LDX #$03                 ; offset
  STA HERO_SPRITE_ADDR, X  ; write sprite-0 x-coord

  LDX #$0b                 ; offset
  STA HERO_SPRITE_ADDR, X  ; write sprite-2 x-coord

  CLC
  ADC #$08

  LDX #$07                 ; offset
  STA HERO_SPRITE_ADDR, X  ; write sprite-1 x-coord

  LDX #$0f                 ; offset
  STA HERO_SPRITE_ADDR, X  ; write sprite-3 x-coord

  PLA
  TAY
  PLA
  TAX
  PLA
  PLP

  RTS
.endproc

.export update_hero_x