processor 6502
        include "vcs.h"
        include "macro.h"
        include "xmacro.h"

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        seg.u Variables
	org $80

Temp	.byte

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	seg Code
        org $f000

Start
	CLEAN_START
        lda #0
        sta Temp

NextFrame
	VERTICAL_SYNC

	TIMER_SETUP 37
        inc Temp
        TIMER_WAIT

	TIMER_SETUP 213

	lda Temp
        and #$7f
        jsr WaitForScanline
        sta COLUBK
        lda #180
        jsr WaitForScanline
	lda #0
        sta COLUBK
	lda #192
        jsr WaitForScanline
        jmp TimerDone

TimerDone
	lda #0
        sta COLUBK

	TIMER_SETUP 30
        TIMER_WAIT
        jmp NextFrame

	align $10
WaitForScanline subroutine
        ldy INTIM	; Fetch timer value
.Wait
        cpy INTIM
        beq .Wait	; Wait for it to change
        sta WSYNC	; Sync with scan line
	cmp Timer2Scanline,y
        bcs WaitForScanline
        rts

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	align $100
Timer2Scanline
	.byte 215,  0,214,213,212,211,210,  0,209,208,207,206,205,204,  0,203 
	.byte 202,201,200,199,  0,198,197,196,195,194,  0,193,192,191,190,189 
	.byte 188,  0,187,186,185,184,183,  0,182,181,180,179,178,  0,177,176 
	.byte 175,174,173,172,  0,171,170,169,168,167,  0,166,165,164,163,162 
	.byte   0,161,160,159,158,157,156,  0,155,154,153,152,151,  0,150,149 
	.byte 148,147,146,  0,145,144,143,142,141,140,  0,139,138,137,136,135 
	.byte   0,134,133,132,131,130,  0,129,128,127,126,125,124,  0,123,122 
	.byte 121,120,119,  0,118,117,116,115,114,  0,113,112,111,110,109,108 
	.byte   0,107,106,105,104,103,  0,102,101,100, 99, 98,  0, 97, 96, 95 
	.byte  94, 93, 92,  0, 91, 90, 89, 88, 87,  0, 86, 85, 84, 83, 82,  0 
	.byte  81, 80, 79, 78, 77, 76,  0, 75, 74, 73, 72, 71,  0, 70, 69, 68 
	.byte  67, 66,  0, 65, 64, 63, 62, 61, 60,  0, 59, 58, 57, 56, 55,  0 
	.byte  54, 53, 52, 51, 50,  0, 49, 48, 47, 46, 45, 44,  0, 43, 42, 41 
	.byte  40, 39,  0, 38, 37, 36, 35, 34,  0, 33, 32, 31, 30, 29, 28,  0 
	.byte  27, 26, 25, 24, 23,  0, 22, 21, 20, 19, 18,  0, 17, 16, 15, 14 
	.byte  13, 12,  0, 11, 10,  9,  8,  7,  0,  6,  5,  4,  3,  2,  0,  1

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; Epilogue
	org $fffc
        .word Start
        .word Start