diff options
Diffstat (limited to 'src/driver.s')
| -rw-r--r-- | src/driver.s | 47 |
1 files changed, 28 insertions, 19 deletions
diff --git a/src/driver.s b/src/driver.s index 8b366b7..421dd69 100644 --- a/src/driver.s +++ b/src/driver.s @@ -55,23 +55,21 @@ ;; Same as `zp_next_bullet_cycle` but for enemies. zp_next_enemy_cycle = $37 - ;; Whether sprites have already been moved out in the 'move_sprites_out' - ;; situation. It's probably a waste of resources to spend a full byte for - ;; this, but I didn't see where to put it either, and we still have plenty - ;; of RAM left. - zp_moved_out = $38 - - ;; Whether the pause message on the HUD has to be toggled. Like - ;; 'zp_moved_out', maybe a waste of resource to dedicate a full byte for - ;; this, but we have plenty of RAM left. - zp_pause_toggle = $39 + ;; Bitmap of various boolean values lumped together. + ;; + ;; |SP-- ----| + ;; | + ;; |- S: whether sprites have already been moved out in the + ;; | 'move_sprites_out' situation. + ;; |- P: whether the pause message on the HUD has to be toggled. + zp_flags = $38 ;; Initialization routine that is to be called before enabling NMIs back for ;; the first time. .proc init_before_nmi lda #0 - sta Driver::zp_pause_toggle sta Driver::zp_blink_status + sta Driver::zp_flags rts .endproc @@ -173,8 +171,9 @@ ;; Set that we have done this operation so it's not done in future ;; cycles. - lda #1 - sta Driver::zp_moved_out + lda Driver::zp_flags + ora #$80 + sta Driver::zp_flags rts .endproc @@ -222,10 +221,14 @@ jsr Explosions::init jsr Items::init - ;; Initialize pause timer and some boolean values. + ;; Initialize pause timer. lda #0 sta zp_pause_timer - sta Driver::zp_moved_out + + ;; Clear out the 'S' flag. + lda Driver::zp_flags + and #$7F + sta Driver::zp_flags ;; Initialize variables for sprite cycling. sta zp_next_bullet_cycle @@ -257,8 +260,9 @@ sta zp_pause_timer ;; Toggle the message on the HUD. - lda #1 - sta Driver::zp_pause_toggle + lda Driver::zp_flags + ora #$40 + sta Driver::zp_flags ;; Pause vs unpause. lda #%00001000 @@ -310,8 +314,8 @@ beq @sprite_cycling ;; Invalidate bullets and enemies if we haven't already. - lda Driver::zp_moved_out - bne @check_explosions + bit Driver::zp_flags + bmi @check_explosions jsr move_sprites_out @check_explosions: @@ -625,6 +629,11 @@ ;; ;; NOTE: only call this function from NMI code. .proc hud_toggle_pause + ;; Unset the 'P' flag. + lda Driver::zp_flags + and #%10111111 + sta Driver::zp_flags + lda #%00001000 and Globals::zp_flags bne @paused |