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.segment "CODE"
;; All the functions and variables which are related to the title screen.
.scope Title
;; Y and X coordinates for the sprite that guides the player on the menu.
SPRITE_Y_POSITION0 = $A7
SPRITE_Y_POSITION1 = $BF
SPRITE_X_POSITION = $40
;; The title has a timer as a delay between joypad presses from the player.
TIMER_INIT_VALUE = (HZ / 3)
zp_title_timer = $30
;; Initialize all the elements for the title screen.
.proc init
lda #0
sta zp_title_timer
;; Initialize the sprite that guides the player on the menu.
lda #SPRITE_Y_POSITION0
sta OAM::m_sprites
lda #$30
sta OAM::m_sprites + 1
lda #$00
sta OAM::m_sprites + 2
lda #SPRITE_X_POSITION
sta OAM::m_sprites + 3
rts
.endproc
;; Checks the pressed buttons from the joypad and moves the sprite for the
;; menu accordingly.
;;
;; Returns 1 if the player hit start and the game can start, 0 otherwise.
.proc update
lda zp_title_timer
bne @end
lda #Joypad::BUTTON_UP
and Joypad::zp_buttons1
beq @check_down
lda #SPRITE_Y_POSITION0
cmp OAM::m_sprites
beq @end
sta OAM::m_sprites
jmp @set_timer_and_end
@check_down:
lda #Joypad::BUTTON_DOWN
and Joypad::zp_buttons1
beq @check_select
lda #SPRITE_Y_POSITION1
cmp OAM::m_sprites
beq @end
sta OAM::m_sprites
jmp @set_timer_and_end
@check_select:
lda #Joypad::BUTTON_SELECT
and Joypad::zp_buttons1
bne @do_select
;; If none of the above has been pressed, our only possibility is the
;; start button. If that's the case, jump there, otherwise quit.
lda #(Joypad::BUTTON_START | Joypad::BUTTON_A)
and Joypad::zp_buttons1
beq @end
JAL start
@do_select:
lda #SPRITE_Y_POSITION0
cmp OAM::m_sprites
beq @down
sta OAM::m_sprites
bne @set_timer_and_end
@down:
lda #SPRITE_Y_POSITION1
sta OAM::m_sprites
@set_timer_and_end:
lda #TIMER_INIT_VALUE
sta zp_title_timer
@end:
lda #0
rts
.endproc
;; Save the selection from the menu, hide all elements from the title
;; screen, and return always 1.
.proc start
;; Select whether player 2 is to be alive or not.
lda #%00000010
ldx OAM::m_sprites
cpx #SPRITE_Y_POSITION1
bne @set_multi
ora #%10000100
@set_multi:
sta Globals::zp_multiplayer
;; Hide the sprite from the menu.
lda #$EF
sta OAM::m_sprites
lda #1
rts
.endproc
.endscope
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