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https://github.com/deater/dos33fsprogs.git
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190 lines
2.0 KiB
ArmAsm
190 lines
2.0 KiB
ArmAsm
; particle effect? -- Apple II Lores
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; by Vince `deater` Weaver
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PARTICLES = 128
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SCALE = 2
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COLOR = $30
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QUOTIENT = $FA
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DIVISOR = $FB
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DIVIDEND = $FC
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XX = $FD
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YY = $FE
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FRAME = $FF
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FULLGR = $C052
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LORES = $C056 ; Enable LORES graphics
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HGR2 = $F3D8
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HGR = $F3E2
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PLOT = $F800 ; PLOT AT Y,A (A colors output, Y preserved)
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SETGR = $FB40
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WAIT = $FCA8 ; delay 1/2(26+27A+5A^2) us
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particle_x = $2000
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particle_y = $2100
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particle_life = $2200
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particle_vx = $2300
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particle_vy = $2400
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particle_decay = $2600
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particle:
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jsr SETGR
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bit FULLGR
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; init
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ldx #PARTICLES
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init_particles_loop:
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jsr init_particle
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dex
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bpl init_particles_loop
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main_loop:
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lda #200
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jsr WAIT
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; clear screen
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ldx #0
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lda #$8
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sta clear_loop_smc+2
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lda #0
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clear_loop:
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clear_loop_smc:
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sta $400,X
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dex
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bne clear_loop
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dec clear_loop_smc+2
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ldy clear_loop_smc+2
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cpy #3
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bne clear_loop
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; move particles
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; draw particles
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ldx #PARTICLES
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draw_particles_loop:
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; adjust x
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lda particle_x,X
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clc
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adc particle_vx,X
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sta particle_x,X
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bmi redo_particle
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cmp #40*SCALE
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bcs redo_particle
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; adjust y
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; first adjust for gravity
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inc particle_vy,X
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; inc particle_vy,X
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lda particle_y,X
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clc
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adc particle_vy,X
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sta particle_y,X
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bmi redo_particle
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cmp #48*SCALE
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bcc y_good
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redo_particle:
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jsr init_particle
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y_good:
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lda particle_life,X
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sta COLOR
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sec
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sbc #$11
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sta particle_life,X
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cmp #$ef
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beq redo_particle
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lda particle_x,X
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lsr
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tay
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lda particle_y,X
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lsr
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jsr PLOT ; PLOT AT Y,A
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dex
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bpl draw_particles_loop
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jmp main_loop
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; init particle
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; particle in X
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init_particle:
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; source
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lda #20*SCALE
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sta particle_x,X
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lda #10*SCALE
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sta particle_y,X
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; color
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lda #$ff
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sta particle_life,X
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; velocities
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; -8 to 8?
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jsr random
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cmp #$80
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ror
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sta particle_vx,X
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jsr random
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sta particle_vy,X
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; we don't actually use this?
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; lda #32
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; sta particle_decay,X
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rts
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; -8 to 8
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random:
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inc random_smc+1
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bne noflo
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inc random_smc+2
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beq noflo
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lda #$d0
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sta random_smc+2
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noflo:
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random_smc:
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lda $d000
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and #$f
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sec
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sbc #$8
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rts
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; need this to be at $3F5
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jmp particle
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