diff options
Diffstat (limited to 'src/enemies.s')
| -rw-r--r-- | src/enemies.s | 66 |
1 files changed, 44 insertions, 22 deletions
diff --git a/src/enemies.s b/src/enemies.s index 021a3bc..23ae18f 100644 --- a/src/enemies.s +++ b/src/enemies.s @@ -67,8 +67,10 @@ zp_enemy_arg = $D5 ;; Values for the counter of enemies that fall. - FALLING_VELOCITY = HZ / 10 - FALLING_VELOCITY_FAST = FALLING_VELOCITY / 2 + FALLING_VELOCITY_0 = HZ / 5 + FALLING_VELOCITY_1 = HZ / 10 + FALLING_VELOCITY_2 = HZ / 25 + FALLING_VELOCITY_3 = HZ / 50 ;; Initializes all the enemies for the current level. That is, it prepares ;; all the movement handlers, the enemy tiles to be used, and initializes @@ -93,7 +95,7 @@ ;; TODO: rest of the enemies. ;; TODO: there are ways to optimize this txa - beq @init_basic_1 + beq @init_basic cmp #1 beq @init_bounce_1 cmp #2 @@ -103,17 +105,14 @@ cmp #5 beq @init_bounce_2 cmp #6 - beq @init_basic_2 + __fallthrough__ @init_basic - @init_basic_1: + @init_basic: lda #1 sta Enemies::zp_enemy_arg - lda #FALLING_VELOCITY - bne @set - @init_basic_2: - lda #2 - sta Enemies::zp_enemy_arg - lda #FALLING_VELOCITY_FAST + jsr Prng::random_valid_y_coordinate + and #$0F + ora #$11 bne @set @init_erratic: lda #1 @@ -434,12 +433,14 @@ ;; Basic falling movement. Straight horizontal movement with a slight ;; downward angle. Enemy should explode on platform/ground contact. The - ;; 'extra' state is used as a counter for the falling velocity (i.e. enemy - ;; falls 1 pixel per counter exhaustion). - ;; TODO: extra |TTTT KK-D| - ;; timer - ;; kind of movement - ;; downwards/upwards + ;; 'extra' state is defined as follows: + ;; + ;; |TTTT KK-D|; where: + ;; | + ;; |- D: downwards if 1; upwards if 0 (just like the 'diagonal' algorithm). + ;; |- K: movement kind (see the constants FALLING_VELOCITY_*). + ;; |- T: timer. Whenever it reaches zero, then a vertical movement is done. + ;; .proc basic ;; First of all, we always move enemies horizontally, while being ;; mindful on the direction and the step depending on the enemy type. @@ -462,23 +463,44 @@ ;; collision checking. @do_counter: lda Enemies::zp_enemies_pool_base + 3, x + tay sec - sbc #1 + sbc #$10 + and #$F0 bne @update_extra_state ;; Move downwards and reset the 'extra' state depending on the enemy ;; kind. - @downward: inc Enemies::zp_enemies_pool_base + 1, x - lda Globals::zp_level_kind + ;; Yes, doing an index on a pre-computed ROM table would've been faster, + ;; but I need the 'x' register and I didn't feel like doing funny + ;; dances when it's not so bad. + tya + and #$0C beq @init_zero - lda #FALLING_VELOCITY_FAST + cmp #$04 + beq @init_one + cmp #$08 + beq @init_two + lda #(FALLING_VELOCITY_3 << 4) bne @update_extra_state @init_zero: - lda #FALLING_VELOCITY + lda #(FALLING_VELOCITY_0 << 4) + bne @update_extra_state + @init_one: + lda #(FALLING_VELOCITY_1 << 4) + bne @update_extra_state + @init_two: + lda #(FALLING_VELOCITY_2 << 4) @update_extra_state: + ;; Save the new timer into a temporary value, mask out the high byte + ;; from the original value, and then merge the values. + sta Globals::zp_tmp0 + tya + and #$0F + ora Globals::zp_tmp0 sta Enemies::zp_enemies_pool_base + 3, x ;; Check collisions with the background. |