mirror of
https://github.com/catseye/SixtyPical.git
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161 lines
3.3 KiB
Plaintext
161 lines
3.3 KiB
Plaintext
assign byte table actor_0_sprite_x 60
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assign byte table actor_0_sprite_y 68
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assign byte table vic_sprite_0_x 53281
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assign byte table vic_sprite_0_y 53289
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reserve byte actor_msb
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reserve byte msb_counter
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reserve vector logic_vector
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assign byte vic_sprite_x_msb 55555
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routine main {
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jsr display_actors
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}
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routine display_actors {
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ldy #0
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ldx #0
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repeat bne {
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lda actor_0_sprite_x, y
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sta vic_sprite_0_x, x
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lda actor_0_sprite_y, y
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sta vic_sprite_0_y, x
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iny
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inx
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inx
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cpy #8
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}
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lda actor_msb
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sta vic_sprite_x_msb
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}
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routine update_actors {
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lda #1
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sta msb_counter
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lda #0
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sta actor_msb
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ldy #0
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repeat ... {
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lda actor_0_logic_high, y
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if bne {
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sta logic_vector+1
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lda actor_0_logic_low, y
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sta logic_vector
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save y
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jsr logic_vector
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restore y
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}
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// update_xvel
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clc
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lda actor_0_xvel, y
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adc actor_0_xacc, y
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cmp #max_vel
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bcc xvel_within_limit ; branch if accumulator is less
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cmp #min_vel
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bcs xvel_within_limit ; branch if accumulator is greater or equal
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jmp update_xpos
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xvel_within_limit:
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sta actor_0_xvel, y
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update_xpos:
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clc
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lda actor_0_xpos_low, y
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adc actor_0_xvel, y
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sta actor_0_xpos_low, y
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lda #0
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sta sign_extend
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lda actor_0_xvel, y
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and #$80
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beq carry_x
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dec sign_extend
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carry_x:
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lda actor_0_xpos_high, y
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adc sign_extend ; $00, or $ff if xvel < 0
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sta actor_0_xpos_high, y
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update_yvel:
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clc
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lda actor_0_yvel, y
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adc actor_0_yacc, y
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cmp #max_vel
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bcc yvel_within_limit ; branch if accumulator is less
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cmp #min_vel
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bcs yvel_within_limit ; branch if accumulator is greater or equal
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jmp update_ypos
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yvel_within_limit:
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sta actor_0_yvel, y
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update_ypos:
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clc
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lda actor_0_ypos_low, y
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adc actor_0_yvel, y
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sta actor_0_ypos_low, y
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lda #0
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sta sign_extend
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lda actor_0_yvel, y
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and #$80
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beq carry_y
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dec sign_extend
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carry_y:
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lda actor_0_ypos_high, y
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adc sign_extend
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sta actor_0_ypos_high, y
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precompute_sprite_position:
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lda actor_0_xpos_low, y
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sta temp_low
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lda actor_0_xpos_high, y
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sta temp_high
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jsr shift_temp
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jsr shift_temp
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jsr shift_temp
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sta actor_0_sprite_x, y
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lda temp_high ; calculate the sprite's msb
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beq advance_msb_counter
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lda actor_msb
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ora msb_counter
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sta actor_msb
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advance_msb_counter:
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asl msb_counter
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set_sprite_y:
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lda actor_0_ypos_low, y
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sta temp_low
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lda actor_0_ypos_high, y
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sta temp_high
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jsr shift_temp
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jsr shift_temp
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jsr shift_temp
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sta actor_0_sprite_y, y
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next_actor:
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cpy #$07
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beq exit_actor_loop
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iny
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jmp update_actor_loop
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exit_actor_loop:
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rts
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