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dos33fsprogs/waterfall/waterfall_simple.s

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; Lo-res cycle-counting water transparency hack
; by deater (Vince Weaver) <vince@deater.net>
; Zero Page
FRAMEBUFFER = $00 ; $00 - $0F
YPOS = $10
YPOS_SIN = $11
CH = $24
CV = $25
GBASL = $26
GBASH = $27
BASL = $28
BASH = $29
MASK = $2E
COLOR = $30
FRAME = $60
MB_VALUE = $91
BIRD_STATE = $E0
BIRD_DIR = $E1
DRAW_PAGE = $EE
LASTKEY = $F1
PADDLE_STATUS = $F2
XPOS = $F3
TEMP = $FA
TEMPY = $FB
INL = $FC
INH = $FD
OUTL = $FE
OUTH = $FF
; Soft Switches
KEYPRESS= $C000
KEYRESET= $C010
SET_GR = $C050 ; Enable graphics
FULLGR = $C052 ; Full screen, no text
PAGE0 = $C054 ; Page0
PAGE1 = $C055 ; Page1
LORES = $C056 ; Enable LORES graphics
PADDLE_BUTTON0 = $C061
PADDL0 = $C064
PTRIG = $C070
; ROM routines
TEXT = $FB36 ;; Set text mode
HOME = $FC58 ;; Clear the text screen
WAIT = $FCA8 ;; delay 1/2(26+27A+5A^2) us
; location we don't care about
DUMMY = $300
waterfall_demo:
;===================
; init screen
jsr TEXT
jsr HOME
bit PAGE0
;===================
; init vars
lda #0
sta BIRD_DIR
sta BIRD_STATE
sta FRAME
lda #4
sta DRAW_PAGE
sta XPOS
;===================
; Mockingboard
jsr mockingboard_init
; Enable channel A tone+noise
ldx #7 ; 2
lda #$36 ; 2
sta MB_VALUE ; 3
jsr write_ay_both ; 6+65
;=============================
; Load foreground to graphic page1 (apple page2)
lda #$0c
sta BASH
lda #$00
sta BASL ; load image to $c00
lda #<waterfall_page1
sta GBASL
lda #>waterfall_page1
sta GBASH
jsr load_rle_gr
jsr gr_copy_to_current ; copy to page1
;=============================
; Load bg to memory
lda #$0c
sta BASH
lda #$00
sta BASL ; load image to $c00
lda #<waterfall_page2
sta GBASL
lda #>waterfall_page2
sta GBASH
jsr load_rle_gr
;==============================
; setup graphics for vapor lock
;==============================
; Clear Page0 to all green
lda #$0
sta DRAW_PAGE
lda #$44
jsr clear_gr
; Make top half of screen blue, down to line 26
lda #$11
ldy #24
jsr clear_page_loop
;=====================================================
; attempt vapor lock
; by reading the "floating bus" we can see most recently
; written value of the display
; we look for $55 (which is the grey line)
;=====================================================
; See:
; Have an Apple Split by Bob Bishop
; Softalk, October 1982
; Challenges: each scan line scans 40 bytes.
; The blanking happens at the *beginning*
; So 65 bytes are scanned, starting at adress of the line - 25
; the scan takes 8 cycles, look for 4 repeats of the value
; to avoid false positive found if the horiz blanking is mirroring
; the line (max 3 repeats in that case)
vapor_lock_loop: ; first make sure we have all blue
lda #$11 ; 2
zxloop:
ldx #$04 ; 2
wiloop:
cmp $C051 ; 4
bne zxloop ; 2/3
dex ; 2
bne wiloop ; 2/3
lda #$44 ; now look for our color (4 times) ; 2
zloop:
ldx #$04 ; 2
; what cycle does CMP happen at?
; while matching match = 4+2+2+3 = 11???
; if start at x=0, 0, 11, 22, 33 exit at 43
; if start at x=1, 1, 12, 23, 34 exit at 44
; if start at x=2, 2, 13, 24, 35 exit at 45
; if start at x=3, 3, 14, 25, 36 exit at 46
; if start at x=4, 4, 15, 26, 37 exit at 47
; if start at x=5, 5, 16, 27, 38 exit at 48
; if start at x=6, 6, 17, 28, 39 exit at 49
; if start at x=7, 7, 18, 29, *40 exit at **
; if start at x=8, 8, 19, 30, *41 exit at **
; if not match, 2+4+3 = 9, first match = 8
qloop:
cmp $C051 ; 4
bne zloop ; 2/3
dex ; 2
bne qloop ; 2/3
; found first line of black after green, at up to line 26 on screen
; so we want roughly 22 lines * 4 = 88*65 = 5720 + 4550 = 10270
; - 65 (for the scanline we missed) = 10205 - 12 = 10193
jsr gr_copy_to_current ; 6+ 9292
; 10193 - 9298 = 895
; Fudge factor (unknown) -30 = 865
; GR part
bit LORES ; 4
bit SET_GR ; 4
bit FULLGR ; 4
; Try X=88 Y=2 cycles=893 R2
nop ; 2
ldy #2 ; 2
loopA:
ldx #88 ; 2
loopB:
dex ; 2
bne loopB ; 2nt/3
dey ; 2
bne loopA ; 2nt/3
jmp display_loop
.align $100
;================================================
; Display Loop
;================================================
; each scan line 65 cycles
; 1 cycle each byte (40cycles) + 25 for horizontal
; Total of 12480 cycles to draw screen
; Vertical blank = 4550 cycles (70 scan lines)
; Total of 17030 cycles to get back to where was
; if even, 10 + 9 + display_even + 2 (balance) = 21+display_even
; if odd 10 + 8 + display_odd + 3 (balance) = 21+display_odd
; we have 3 (the jmp) + 6 (the rts) - 1 (fallthrough)
; = 8 cycles that need to be eaten by the vblank
display_loop:
inc FRAME ; 5
lda FRAME ; 3
and #$10 ; 2
beq even
; 2
lda FRAME ; (nop) ; 3
jsr display_odd ; 6
jmp vblank ; 3
even:
; 3
nop ; (nop) ; 2
jsr display_even ; 6
jmp vblank ; 3
vblank:
;======================================================
; We have 4550 cycles in the vblank, use them wisely
;======================================================
; do_nothing should be 4550
; -9 letfover from HBLANK code
; -49 check for keypress
; -2252 copy screen
; -2231 draw sprite
; =============
; 9 cycles
; jsr do_nothing ; 6
; 17 cycles
inc YPOS ; 5
nop
nop
; inc YPOS ; 5
; inc YPOS ; 5
; nop ; 2
; nop ; 2
;=========================
; Clear background
;=========================
jsr gr_copy_row22 ; 6+ 2246
;=========
; 2252
;==========================
; draw bird sprite
;==========================
; 8 prefix
; bird_walk_right= 14 + 2175 2206 (need 17)
; bird_stand_right= 13 + 2190 2206 (need 3)
; bird_walk_left= 15 + 2175 2206 (need 16)
; bird_stand_left= 14 + 2190 2206 (need 2)
; call to sprite 17 postfix
;====================================================
; 2231
lda BIRD_STATE ; 3
and #1 ; 2
ldx BIRD_DIR ; 3
bne bird_left
bird_right:
; 2
cmp #1 ; 2
beq bird_walk_right
; 2
bird_stand_right:
ldx #>bird_rider_stand_right ; 2
ldy #<bird_rider_stand_right ; 2
lda YPOS ; nop=3
jmp draw_bird ; 3
bird_walk_right:
; 3
ldx #>bird_rider_walk_right ; 2
ldy #<bird_rider_walk_right ; 2
jmp kill_less_time ; 3
bird_left:
; 3
cmp #1 ; 2
beq bird_walk_left
bird_stand_left:
; 2
ldx #>bird_rider_stand_left ; 2
ldy #<bird_rider_stand_left ; 2
nop ; nop=2
jmp draw_bird ; 3
bird_walk_left:
; 3
ldx #>bird_rider_walk_left ; 2
ldy #<bird_rider_walk_left ; 2
kill_time:
nop ; 2 ; need to kill 16
kill_less_time:
lda YPOS ; nop=3 ; need to kill 14
lda YPOS ; nop=3
lda YPOS ; nop=3
lda YPOS ; nop=3
nop ; 2
jmp draw_bird ; 3
draw_bird:
stx INH ; 3
sty INL ; 3
lda #22 ; 2
sta YPOS ; 3
jsr put_sprite ; 6
;=========
; 17 + 2190
;====================
; Handle keypresses
; if no keypress, 9
; if keypress, 6+43 = 49
lda KEYPRESS ; 4
bmi keypress
; 2
no_keypress:
; kill 40 cycles
ldx #0 ; 2
inc YPOS,X ; 6
inc YPOS,X ; 6
inc YPOS,X ; 6
inc YPOS,X ; 6
inc YPOS,X ; 6
inc YPOS,X ; 6
nop ; 2
jmp display_loop ; 3
;===================================================
; key was pressed handling takes 12 + 20 + 11 = 43
keypress:
; 1
bit KEYRESET ; 4
inc BIRD_STATE ; 5
and #$5f ; mask keypress ; 2
is_it_right:
cmp #$15 ; right arrow ; 2
bne is_it_left
; 2
inc XPOS ; 5
lda #0 ; 2
sta BIRD_DIR ; 3
lda YPOS ; 3-cycle nop ; 3
convoluted:
jmp adjust_xpos ; 3 ; 20 if right
is_it_left:
; 5
cmp #$8 ; left arrow ; 2
beq is_left
; 2
nop ; 2
lda YPOS ; 3-cycle nop
jmp convoluted ; 3
; ------ 20 if neither
is_left:
; 3
dec XPOS ; 5 ; 20 if left
lda #1 ; 2
sta BIRD_DIR ; 3
adjust_xpos:
lda XPOS ; 3
and #$1f ; keep in 0-31 range ; 2
sta XPOS ; 3
jmp display_loop ; 3
;=================================
; do nothing
;=================================
; and take 11-6 = 5 cycles to do it
;do_nothing:
; Try X=3 Y=1 cycles=22
; nop ; 2
; nop ; 2
; ldy #1 ; 2
;loop1:
; ldx #3 ; 2
;loop2:
; dex ; 2
; bne loop2 ; 2nt/3
; dey ; 2
; bne loop1 ; 2nt/3
; rts ; 6
;==================================
; HLINE
;==================================
; Color in A
; Y has which line
hline:
pha ; 3
ldx gr_offsets,y ; 4+
stx hline_loop+1 ; 4
lda gr_offsets+1,y ; 4+
clc ; 2
adc DRAW_PAGE ; 3
sta hline_loop+2 ; 4
pla ; 4
ldx #39 ; 2
hline_loop:
sta $5d0,X ; 38 ; 5
dex ; 2
bpl hline_loop ; 2nt/3
rts ; 6
;==========================
; Clear gr screen
;==========================
; Color in A
clear_gr:
ldy #46
clear_page_loop:
jsr hline
dey
dey
bpl clear_page_loop
rts
gr_offsets:
.word $400,$480,$500,$580,$600,$680,$700,$780
.word $428,$4a8,$528,$5a8,$628,$6a8,$728,$7a8
.word $450,$4d0,$550,$5d0,$650,$6d0,$750,$7d0
.include "../asm_routines/gr_unrle.s"
.include "../asm_routines/keypress.s"
.include "gr_copy.s"
.include "gr_unrolled_copy.s"
.include "put_sprite.s"
.include "mockingboard.s"
.include "waterfall_page1.inc"
.include "waterfall_page2.inc"
.align $100
.include "tfv_sprites.inc"
.align $100
;=================================
; Display Odd
;=================================
; we have 65 cycles per line
; the first 25 are in hblank
; we come in already 21 cycles into things
; so the first scanline is a loss (but that's OK)
; first scanline: 21+ 2 (from ldy) so need to kill 65-23 = 42
; second scanline, again kill so 65 killed
display_odd:
odd_first_four_lines:
; line 0
; 21
ldy #4 ; 2
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
; line 1, 65 cycles
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; line 2, 65 cycles
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; line 3, 65 cycles
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
odd_twinkle_stars:
twinkle_loop_odd:
; line 0
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq twinkle_loop_odd_done ;
; 2
jmp twinkle_loop_odd ; 3
twinkle_loop_odd_done:
ldy #31 ; 2
falls_loop_odd:
; line 0
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq falls_loop_odd_done ;
; 2
jmp falls_loop_odd ; 3
falls_loop_odd_done:
; 3
ldy #12 ; 2
ground_loop_odd:
; line 0
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq ground_loop_odd_done ;
; 2
jmp ground_loop_odd ; 3
ground_loop_odd_done:
; 3
nop ; 2
rts ; 6
.align $100
;=================================
; Display Even
;=================================
; we have 65 cycles per line
; the first 25 are in hblank
; we come in already 21 cycles into things
; so the first scanline is a loss (but that's OK)
; first scanline: 21+ 2 (from ldy) so need to kill 65-23 = 42
; second scanline, again kill so 65 killed
display_even:
even_first_four_lines:
; we do mockingboard here
; we have 239 cycles (65*4 = 260 - 21 = 239)
; 78+78+2+20 = 178
; 239 - 178 = 61 to kill
; come in with 21
; 21
; kill 61
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda XPOS ; 3
nop ; 2
nop ; 2
; high = 5 + 12+ 3 = 20
; medium = 5 + 9 + 6 = 20
; low = 5 + 9 + 6 = 20
lda XPOS ; 3
cmp #23 ; 2
bmi check_medium
; 2
lda #35 ; 2
sec ; 2
sbc XPOS ; 3
sta YPOS ; (nop) ; 3
was_low:
jmp write_volume ; 3
check_medium:
; 3
nop ; 2
nop ; 2
cmp #12 ; 2
bmi was_low
was_medium:
; 2
lda #12 ; 2
nop ; 2
write_volume:
; write A volume
sta MB_VALUE ; 3
ldx #8 ; 2
lda #$2 ; 2
jsr write_ay_both ; 6+65
;===============
; 78
; write noise
ldx #6 ; 2
lda #0 ; 2
sta MB_VALUE ; 3
jsr write_ay_both ; 6+65
;===============
; 78
; setup loop for next section
ldy #4 ; 2
even_twinkle_stars:
twinkle_loop_even:
; line 0
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq twinkle_loop_even_done ;
; 2
jmp twinkle_loop_even ; 3
twinkle_loop_even_done:
ldy #31 ; 2
falls_loop_even:
; line 0
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE0 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq falls_loop_even_done ;
; 2
jmp falls_loop_even ; 3
falls_loop_even_done:
; 3
ldy #12 ; 2
ground_loop_even:
; line 0
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; endfalls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 2
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 3
bit PAGE0 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE0 ; 4
lda YPOS ; 3
bit PAGE0 ; 4
; end falls
; delay 21
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
; line 4
bit PAGE1 ; 4
; delay 29
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
asl DUMMY ; 6
lda YPOS ; 3
nop ; 2
; falls
bit PAGE1 ; 4
lda YPOS ; 3
bit PAGE1 ; 4 ; 44
; end falls
; delay 21 - 7 from loop
asl DUMMY ; 6
asl DUMMY ; 6
nop ; 2 ; 58
dey ; 2
beq ground_loop_even_done ;
; 2
jmp ground_loop_even ; 3
ground_loop_even_done:
; 3
nop ; 2
rts ; 6
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