diff options
Diffstat (limited to 'src/enemies.s')
| -rw-r--r-- | src/enemies.s | 122 |
1 files changed, 80 insertions, 42 deletions
diff --git a/src/enemies.s b/src/enemies.s index 9aaddbe..0ea0e50 100644 --- a/src/enemies.s +++ b/src/enemies.s @@ -10,7 +10,40 @@ inx .endmacro +;; Increase the value from the enemy indexed by ADDR and the 'x' register on the +;; pool. The value will be increased at the same rate on PAL and on NTSC, even +;; if the way to guarantee that is different between these two versions. +.macro INC_MOVEMENT_X ADDR + .ifdef PAL + lda ADDR, x + clc + adc Enemies::zp_movement_arg + sta ADDR, x + .else + inc ADDR, x + .endif +.endmacro + +;; Decrease the value from the enemy indexed by ADDR and the 'x' register on the +;; pool. The value will be decreased at the same rate on PAL and on NTSC, even +;; if the way to guarantee that is different between these two versions. +.macro DEC_MOVEMENT_X ADDR + .ifdef PAL + lda ADDR, x + sec + sbc Enemies::zp_movement_arg + sta ADDR, x + .else + dec ADDR, x + .endif +.endmacro + .scope Enemies + .ifdef PAL + ;; Shadowed from 'Driver::zp_pal_counter'. + zp_pal_counter = $31 ; asan:ignore + .endif + ;; Maximum amount of enemies allowed on screen at the same time. ;; ;; NOTE: EXPLOSIONS_POOL_CAPACITY depends on this value. If you update this, @@ -64,8 +97,12 @@ ;; the movement handler. Check the documentation on movement handlers. zp_pool_index = $D4 - ;; An extra argument that enemies can have depending on their type. This is - ;; useful for different waves with the same algorithm but different speeds. + ;; An extra argument for enemies which depends on their type. This is used + ;; in two ways: + ;; 1. Make the PAL version the same as NTSC (by incrementing its value + ;; when needed to match it). + ;; 2. Re-use the same algorithms for different enemies with the same + ;; pattern but different velocities. zp_movement_arg = $D5 ;; The palette to be used in the next enemy initialization. @@ -154,8 +191,15 @@ sta Enemies::zp_movement_fn + 1 ;; Initialize the enemy arg, which is always 1 except for homing - ;; attacks. + ;; attacks. This initialized is increased by one on PAL if the PAL + ;; counter requires it to. ldy #1 + .ifdef PAL + lda Enemies::zp_pal_counter + bne @skip_uptick + iny + @skip_uptick: + .endif cpx #3 bne @set_arg iny @@ -694,16 +738,10 @@ lda Enemies::zp_pool_base, x and #$80 beq @move_left - lda Enemies::zp_pool_base + 2, x - clc - adc Enemies::zp_movement_arg - sta Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 jmp @do_counter @move_left: - lda Enemies::zp_pool_base + 2, x - sec - sbc Enemies::zp_movement_arg - sta Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 ;; Decrement the counter from the 'extra' state. If it reaches zero, ;; then we should do some downward movement. Otherwise we just go to @@ -721,10 +759,10 @@ tya and #$01 beq @up - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 jmp @compute_next_counter @up: - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 @compute_next_counter: ;; Yes, doing an index on a pre-computed ROM table would've been faster, @@ -779,14 +817,14 @@ ;; Perform a collision check with the upper left boundary. jsr Background::collides beq @check_up_right - JAL bite_the_dust + JAL Enemies::bite_the_dust @check_up_right: ;; Increase the X tile coordinate to check for the upper right boundary. inc Globals::zp_arg1 jsr Background::collides beq @check_down - JAL bite_the_dust + JAL Enemies::bite_the_dust @check_down: ;; Now let's go for bottom boundaries. The notion of "bottom" is @@ -803,7 +841,7 @@ ;; And the actual check. jsr Background::collides beq @check_down_left - JAL bite_the_dust + JAL Enemies::bite_the_dust @check_down_left: ;; So now the only corner left is the bottom left one. Adjust the X tile @@ -811,7 +849,7 @@ dec Globals::zp_arg1 jsr Background::collides beq @end - JAL bite_the_dust + JAL Enemies::bite_the_dust @end: rts @@ -826,10 +864,10 @@ lda Enemies::zp_pool_base, x and #$80 beq @move_left - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 jmp @do_vertical @move_left: - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 @do_vertical: ;; The vertical movement works the same way, but taking into account its @@ -839,10 +877,10 @@ lda Enemies::zp_pool_base + 3, x and #$01 beq @move_up - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 jmp @check_collision @move_up: - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 ;; Collision checking. @check_collision: @@ -885,7 +923,7 @@ ;; Move downwards once, which cancels the movement set at the beginning ;; of the function. - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 rts @@ -921,10 +959,10 @@ ;; stucked or other weird situations. and #$80 beq @bounce_left - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 rts @bounce_left: - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 rts ;; Last but not least, let's see if the enemy collides on its bottom @@ -962,7 +1000,7 @@ sta Enemies::zp_pool_base + 3, x ;; Make it bounce up. - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 rts .endproc @@ -1058,10 +1096,10 @@ beq @move_left iny iny - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 jmp @after_horizontal @move_left: - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 @after_horizontal: ;; We store in a temporary value how much the X tile coordinates will @@ -1115,10 +1153,10 @@ ;; stucked or other weird situations. and #$80 beq @bounce_left - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 rts @bounce_left: - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 rts .endproc @@ -1150,7 +1188,7 @@ tay and #$02 beq @zero_state - JAL basic + JAL Enemies::basic ;; It's the first state of the enemy (i.e. just moving up and down). @zero_state: @@ -1191,10 +1229,10 @@ and #$01 beq @go_down - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 jmp @increase_timer @go_down: - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 @increase_timer: tya @@ -1322,10 +1360,10 @@ lda Enemies::zp_pool_base + 3, x and #$80 beq @think_right - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 rts @think_right: - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 rts ;;; @@ -1342,20 +1380,20 @@ ;; Perform vertical motion. and #$01 beq @move_up - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 jmp @move_horizontal @move_up: - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 ;; And now horizontal motion. @move_horizontal: lda Enemies::zp_pool_base, x and #$80 beq @move_left - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 jmp @check_collisions @move_left: - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 ;;; ;; Collision checking is quite similar to the one on bouncing. The @@ -1396,7 +1434,7 @@ ;; Bounce down a bit to cancel the movement we've done, and set the 'D' ;; bit from the 'extra' value to downward movement. ldx Enemies::zp_pool_index - inc Enemies::zp_pool_base + 1, x + INC_MOVEMENT_X Enemies::zp_pool_base + 1 lda Enemies::zp_pool_base + 3, x ora #$01 sta Enemies::zp_pool_base + 3, x @@ -1422,7 +1460,7 @@ ;; Bounce right a bit to cancel the movement we've done, and set the 'D' ;; bit from the 'state' value to right movement. ldx Enemies::zp_pool_index - inc Enemies::zp_pool_base + 2, x + INC_MOVEMENT_X Enemies::zp_pool_base + 2 lda Enemies::zp_pool_base, x ora #$7F sta Enemies::zp_pool_base, x @@ -1432,7 +1470,7 @@ ;; Bounce left a bit to cancel the movement we've done, and set the 'D' ;; bit from the 'state' value to left movement. ldx Enemies::zp_pool_index - dec Enemies::zp_pool_base + 2, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 2 lda Enemies::zp_pool_base, x and #$7F sta Enemies::zp_pool_base, x @@ -1461,7 +1499,7 @@ ;; Bounce up a bit to cancel the movement we've done, and set the 'D' ;; bit from the 'extra' value to upwards movement. ldx Enemies::zp_pool_index - dec Enemies::zp_pool_base + 1, x + DEC_MOVEMENT_X Enemies::zp_pool_base + 1 lda Enemies::zp_pool_base + 3, x and #$FE sta Enemies::zp_pool_base + 3, x |