diff options
Diffstat (limited to 'src/driver.s')
| -rw-r--r-- | src/driver.s | 55 |
1 files changed, 47 insertions, 8 deletions
diff --git a/src/driver.s b/src/driver.s index 149eaa7..60869c8 100644 --- a/src/driver.s +++ b/src/driver.s @@ -23,6 +23,15 @@ ;; the chance to have the highest priority every now and then. zp_next_bullet_cycle = $33 + ;; The index for the first bullet from the bullets pool on sprite cycling. + zp_first_bullet = $34 + + ;; The index for the first enemy from the enemies pool on sprite cycling. + zp_first_enemy = $36 + + ;; Same as `zp_next_bullet_cycle` but for enemies. + zp_next_enemy_cycle = $37 + ;; Switch from the title screen to the main screen. Note that this function ;; is to be called with the PPU disabled. If that's not the case, then it ;; will set the proper values to disable it on the next `nmi` call and set @@ -94,6 +103,7 @@ ;; Initialize variables for sprite cycling. sta zp_next_bullet_cycle + sta zp_next_enemy_cycle @game: ;; Check if the player is toggling the `pause` state. @@ -155,6 +165,9 @@ ;; allocated. ldy #(Player::PLAYER_SPRITES_COUNT * 4) + ;;; + ;; 1. Attempt to allocate the first spot for a bullet. + ;; The 'x' register will index from the different sprite pools. ldx zp_next_bullet_cycle lda Bullets::zp_bullets_pool_base, x @@ -195,7 +208,7 @@ @after_first_bullet: ;; Save the index that was considered for the first bullet. - stx Globals::zp_tmp0 + stx zp_first_bullet ; TODO: why not after the first ldx? ;; Increase the index for the bullets cycling. If wrapping is detected, ;; then it resets this value back to zero. @@ -208,11 +221,38 @@ @set_next_bullets_cycle: stx zp_next_bullet_cycle - ;; TODO: ensure 1 enemy - ;; iny - ;; iny - ;; iny - ;; iny + ;;; + ;; 2. Attempt to allocate the next spot for the first enemy. + + ;; Get the enemy status byte, while also preserving the current enemy + ;; cycle index. + ldx zp_next_enemy_cycle + stx zp_first_enemy + lda Enemies::zp_enemies_pool_base, x + + ;; Is this a valid enemy? + cmp #$FF + beq @after_first_enemy + + ;; Yes! Let's prepare the arguments an allocate an enemy. + lda Enemies::zp_enemies_pool_base + 1, x + sta Globals::zp_arg0 + lda Enemies::zp_enemies_pool_base + 2, x + sta Globals::zp_arg1 + jsr Enemies::allocate_sprite_y + + @after_first_enemy: + ;; Increase the index for the enemies cycling. If wrapping is detected, + ;; then it resets this value back to zero. + ldx zp_first_enemy + inx + inx + inx + cpx #Enemies::ENEMIES_POOL_CAPACITY_BYTES + bne @set_next_enemies_cycle + ldx #0 + @set_next_enemies_cycle: + stx zp_next_enemy_cycle ;; TODO: ensure 1 item ;; iny @@ -220,12 +260,11 @@ ;; iny ;; iny - ;; TODO: rest of bullets ldx #0 @rest_o_bullets: cpx #Bullets::BULLETS_POOL_CAPACITY_BYTES beq @rest_o_enemies - cpx Globals::zp_tmp0 + cpx zp_first_bullet bne @do_bullet inx inx |