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|
.segment "CODE"
.scope Driver
;; Timer for the player to be able to pick up the joypad upon entering the
;; game.
;;
;; NOTE: this memory address is shared with `zp_title_timer`, as they can
;; never conflict with each other.
zp_player_timer = $30
PLAYER_TIMER_VALUE = HZ * 2
.ifdef PAL
;; Frame counter which resets every 5 frames.
zp_pal_counter = $31
.endif
;; Timer for the pause/unpause workflow.
PAUSE_TIMER_VALUE = (HZ / 3)
zp_pause_timer = $32
;; Switch from the title screen to the main street. Note that this function
;; is to be called with the PPU disabled. If that's not the case, then it
;; will set the proper values to disable it on the next `nmi` call and set
;; the `title over` flag. With that, call again this function so the
;; switching is actually performed.
.proc switch
;; Some things from here require the PPU to be disabled. Hence, if
;; that's not the case, disable it now. The `ppu` and the `title over`
;; flags are set as well.
lda PPU::zp_mask
beq @do_switch
lda #%01000100
ora Globals::zp_flags
sta Globals::zp_flags
lda #$00
sta PPU::zp_mask
rts
@do_switch:
;; Get the assets ready for the main screen. That is, make sure that the
;; palettes and such are as desired since the title screen needed
;; another setup.
jsr Assets::prepare_for_main_screen
;; Switch to the other base nametable.
lda #%10001010
sta PPU::zp_control
;; Enable back the PPU.
lda #%00011110
sta PPU::zp_mask
;; Setup the player timer.
.ifdef PARTIAL
lda #1
.else
lda #PLAYER_TIMER_VALUE
.endif
sta zp_player_timer
;; Mark the state of the game as "game". That is, the player has
;; started. Also set the `ppu` flag and unset the `title over` one.
lda #%01000001
ora Globals::zp_flags
and #%11111011
sta Globals::zp_flags
rts
.endproc
.proc update
lda zp_player_timer
beq @game
dec zp_player_timer
beq @load_player
;; TODO: blinking of the selected player (every HZ count?).
rts
@load_player:
jsr Player::init
;; Initialize pause timer.
lda #0
sta zp_pause_timer
@game:
;; Check if the player is toggling the `pause` state.
lda #(Joypad::BUTTON_START | Joypad::BUTTON_SELECT)
and Joypad::zp_buttons1
beq @skip_pause_handling
;; What does the timer say, is the player allowed to do it?
lda zp_pause_timer
bne @skip_pause_handling
;; The timer is zero and the player asked to pause, let's reset the
;; timer.
lda #PAUSE_TIMER_VALUE
sta zp_pause_timer
;; Pause vs unpause.
lda #%00001000
and Globals::zp_flags
bne @unpause
;; Pause: set the flag and skip the update.
lda #%00001000
ora Globals::zp_flags
sta Globals::zp_flags
rts
@unpause:
;; Unset the flag and go to update.
lda #%11110111
and Globals::zp_flags
sta Globals::zp_flags
bne @do_update
@skip_pause_handling:
;; Decrement the pause timer if it's not in a zero value.
lda zp_pause_timer
beq @pause_check
dec zp_pause_timer
@pause_check:
;; Are we paused? If so return before updating.
lda #%00001000
and Globals::zp_flags
beq @do_update
rts
@do_update:
JAL Player::update
.endproc
.ifdef PAL
;; All the code that is needed to fix some values for PAL machines.
.proc pal_handler
;; Check if 5 frames have passed since last counter reset.
lda Driver::zp_pal_counter
cmp #4
beq @do_handle
;; Nope! Reset the player's step on PAL and increase the counter.
lda #1
sta Player::zp_step_on_pal
inc Driver::zp_pal_counter
bne @end
@do_handle:
;; Increase the step just for this frame and reset the counter.
lda Player::zp_step_on_pal
clc
adc #2
sta Player::zp_step_on_pal
lda #0
sta Driver::zp_pal_counter
@end:
rts
.endproc
.endif
.endscope
|
