diff options
Diffstat (limited to 'src/bullets.s')
| -rw-r--r-- | src/bullets.s | 59 |
1 files changed, 43 insertions, 16 deletions
diff --git a/src/bullets.s b/src/bullets.s index 1dd98e0..cdbcafc 100644 --- a/src/bullets.s +++ b/src/bullets.s @@ -1,5 +1,14 @@ .segment "CODE" +;; Assuming that the 'x' register indexes a bullet on its pool, increment the +;; register as many times as to point to the next one. Bound checking is not +;; performed, it's up to the caller to implement that. +.macro NEXT_BULLET_INDEX_X + inx + inx + inx +.endmacro + ;; Function and variables which deal with the pool of bullets that the ;; `driver.s` will use in order to render and deal with bullets on screen. .scope Bullets @@ -68,9 +77,7 @@ lda #$FF @pool_init_loop: sta zp_bullets_pool_base, x - inx - inx - inx + NEXT_BULLET_INDEX_X dey bne @pool_init_loop @@ -119,9 +126,7 @@ ;; are over the total size in memory, we have to roll the `x` back to ;; zero. This is possible because the loop starts at ;; `zp_last_allocated_index`, which is not necessarily 0. - inx - inx - inx + NEXT_BULLET_INDEX_X cpx #BULLETS_POOL_CAPACITY_BYTES bne @find_free_bullet_bucket ldx #0 @@ -190,9 +195,7 @@ bne @move_active_bullet ;; No, go for the next one. - inx - inx - inx + NEXT_BULLET_INDEX_X jmp @move_loop @move_active_bullet: @@ -213,14 +216,16 @@ ;; are done checking for bullets. In this case, if this was the last ;; bullet active, return early. dec zp_bullets_pool_size - beq @end + bne @decrease_y + jmp @end + @decrease_y: dey - beq @end + bne @next_iteration + jmp @end + @next_iteration: ;; We still have active bullets to move, go to the next iteration. - inx - inx - inx + NEXT_BULLET_INDEX_X bne @move_loop @do_move_active_bullet: @@ -282,8 +287,29 @@ inx jmp @move_loop + ;; Enemy collision for this bullet. It's actually easier/faster to just + ;; unroll the loop. @check_enemy_collision: - ;; TODO + lda #Enemies::ENEMY_0_IDX + sta Enemies::zp_pool_index + jsr Enemies::collides + beq @enemy_1 + jsr Enemies::bite_the_dust + jmp @save_bullet_move + @enemy_1: + lda #Enemies::ENEMY_1_IDX + sta Enemies::zp_pool_index + jsr Enemies::collides + beq @enemy_2 + jsr Enemies::bite_the_dust + jmp @save_bullet_move + @enemy_2: + lda #Enemies::ENEMY_2_IDX + sta Enemies::zp_pool_index + jsr Enemies::collides + beq @save_bullet_move + jsr Enemies::bite_the_dust + __fallthrough__ @save_bullet_move @save_bullet_move: ;; Restore back the old value from the 'x' register. @@ -299,7 +325,8 @@ sta zp_bullets_pool_base, x inx dey - bne @move_loop + beq @end + jmp @move_loop @end: rts |