diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/enemies.s | 50 |
1 files changed, 40 insertions, 10 deletions
diff --git a/src/enemies.s b/src/enemies.s index f007c10..64b9545 100644 --- a/src/enemies.s +++ b/src/enemies.s @@ -74,6 +74,9 @@ ;; useful for different waves with the same algorithm but different speeds. zp_enemy_arg = $D5 + ;; The palette to be used in the next enemy initialization. + zp_palette = $D6 + ;; Checking for collision with bullets is actually way faster if after an ;; update we save tile coordinates for each enemy. For this, we only need to ;; save the tile coordinates, but we actually span 4 bytes per enemy. That's @@ -83,6 +86,10 @@ ;; bullets don't have to work out two different indeces for two different ;; structures. Yes, this also means that we are wasting away 6 bytes of RAM, ;; but we can work with that. + ;; + ;; Similarly, palettes to be used for each enemy is also allocated here, + ;; just because of the convenience of the indexing on base 4. Here each + ;; enemy has the palette in 'lda zp_current_tiles + 2, x'. CURRENT_TILES_BYTES = ENEMIES_POOL_CAPACITY * 4 zp_current_tiles = $F0 ; asan:reserve CURRENT_TILES_BYTES @@ -124,13 +131,20 @@ ;; Initialize the tiles buffer by marking it as invalid. Note that we ;; only initialize those positions that are actually needed. That is, ;; the padding is left untouched as we don't care. - lda #$FF - sta Enemies::zp_current_tiles - sta Enemies::zp_current_tiles + 1 - sta Enemies::zp_current_tiles + 4 - sta Enemies::zp_current_tiles + 5 - sta Enemies::zp_current_tiles + 8 - sta Enemies::zp_current_tiles + 9 + ldy #$FF + sty Enemies::zp_current_tiles + sty Enemies::zp_current_tiles + 1 + sty Enemies::zp_current_tiles + 4 + sty Enemies::zp_current_tiles + 5 + sty Enemies::zp_current_tiles + 8 + sty Enemies::zp_current_tiles + 9 + + ;; Initialize the enemy palettes. + iny + sty Enemies::zp_palette + sty Enemies::zp_current_tiles + 2 + sty Enemies::zp_current_tiles + 6 + sty Enemies::zp_current_tiles + 10 ;; Set the movement function for this type. lda movement_lo, x @@ -175,6 +189,14 @@ ;; to store an enemy on the poll (i.e. 4 bytes). ;; NOTE: the 'y' register is not touched. .proc init_enemy_x + ;; Pick the palette to be used for the enemy. + lda Enemies::zp_palette + clc + adc #1 + and #$03 + sta Enemies::zp_palette + sta Enemies::zp_current_tiles + 2, x + ;; The state is set at random. stx Globals::zp_tmp0 jsr Prng::random_valid_y_coordinate @@ -439,6 +461,13 @@ ;; start like this. lda Enemies::zp_enemies_pool_base, x sta Globals::zp_tmp2 + + ;; Push the palette to be used into the stack. This will be pulled down + ;; below. + lda Enemies::zp_current_tiles + 2, x + pha + + ;; Preserve the index on the pool and load the one for enemy tiles. stx Globals::zp_tmp1 ldx zp_enemy_tiles @@ -449,14 +478,15 @@ ;; not the sprite at the PPU level). bit Globals::zp_tmp2 bmi @face_right - lda #0 - beq @set_state + pla + jmp @set_state @face_right: txa clc adc #8 tax - lda #%01000000 + pla + ora #%01000000 @set_state: sta OAM::m_sprites + 2, y ; top left sta OAM::m_sprites + 6, y ; top right |