2017-12-29 04:40:26 +00:00
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.include "zp.inc"
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;===========
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; CONSTANTS
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;===========
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2017-12-29 05:11:38 +00:00
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NUMSTARS EQU 16
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2017-12-29 04:40:26 +00:00
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;=====================
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; Starfield
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;=====================
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;================================
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; Clear screen and setup graphics
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;================================
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jsr clear_screens ; clear top/bottom of page 0/1
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jsr set_gr_page0
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; Initialize the 2kB of multiply lookup tables
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jsr init_multiply_tables
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;===============
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; Init Variables
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;===============
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lda #0
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2017-12-29 05:11:38 +00:00
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sta DRAW_PAGE
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2017-12-29 04:40:26 +00:00
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starfield_loop:
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2017-12-29 05:11:38 +00:00
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;===============
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; draw stars
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;===============
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draw_stars:
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ldx #NUMSTARS
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lda #20
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ldy #20
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;================================
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; put address in GBASL/GBASH
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; Xcoord in A, Ycoord in Y
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sta TEMPY
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lda gr_offsets,Y ; lookup low-res memory address ; 4
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clc ; 2
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adc TEMPY ; 3
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sta GBASL ; 3
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iny ; 2
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lda gr_offsets,Y ; 4
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adc DRAW_PAGE ; add in draw page offset ; 3
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sta GBASH ; 3
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;===========
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;
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ldy #0
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lda #$ff
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sta (GBASL),Y
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dex
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bne draw_stars
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2017-12-29 04:40:26 +00:00
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starfield_keyboard:
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jsr get_key ; get keypress ; 6
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lda LASTKEY ; 3
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cmp #('Q') ; if quit, then return
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bne skipskip
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rts
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skipskip:
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;==================
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; flip pages
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;==================
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jsr page_flip ; 6
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;==================
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; loop forever
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;==================
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jmp starfield_loop ; 3
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;===============================================
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; External modules
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;===============================================
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.include "../asm_routines/hlin_clearscreen.s"
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.include "../asm_routines/pageflip.s"
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.include "../asm_routines/gr_setpage.s"
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.include "../asm_routines/keypress.s"
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.include "../asm_routines/gr_putsprite.s"
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.include "../asm_routines/text_print.s"
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;===============================================
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; Variables
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;===============================================
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.include "../asm_routines/multiply_fast.s"
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2017-12-29 05:11:38 +00:00
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;======================
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; some "random" numbers
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;======================
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random_table:
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.byte 103,198,105,115, 81,255, 74,236, 41,205,186,171,242,251,227, 70
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.byte 124,194, 84,248, 27,232,231,141,118, 90, 46 ,99, 51,159,201,154
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.byte 102, 50, 13,183, 49, 88,163, 90, 37, 93, 5, 23, 88,233, 94,212
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.byte 171,178,205,198,155,180, 84, 17, 14,130,116, 65, 33, 61,220,135
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.byte 112,233, 62,161, 65,225,252,103, 62, 1,126,151,234,220,107,150
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.byte 143, 56, 92, 42,236,176, 59,251, 50,175, 60, 84,236, 24,219, 92
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.byte 2, 26,254, 67,251,250,170, 58,251, 41,209,230, 5, 60,124,148
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.byte 117,216,190, 97,137,249, 92,187,168,153, 15,149,177,235,241,179
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.byte 5,239,247, 0,233,161, 58,229,202, 11,203,208, 72, 71,100,189
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.byte 31, 35, 30,168, 28,123,100,197, 20,115, 90,197, 94, 75,121, 99
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.byte 59,112,100, 36, 17,158, 9,220,170,212,172,242, 27, 16,175, 59
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.byte 51,205,227, 80, 72, 71, 21, 92,187,111, 34, 25,186,155,125,245
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.byte 11,225, 26, 28,127, 35,248, 41,248,164, 27, 19,181,202, 78,232
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.byte 152, 50, 56,224,121, 77, 61, 52,188, 95, 78,119,250,203,108, 5
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.byte 172,134, 33, 43,170, 26, 85,162,190,112,181,115, 59, 4, 92,211
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.byte 54,148,179,175,226,240,228,158, 79, 50, 21, 73,253,130, 78,169
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z_table:
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; 1/16.0 - 1/12.25
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.byte $10,$10,$10,$10,$11,$11,$11,$11,$12,$12,$12,$13,$13,$14,$14,$14
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; 1/12.0 - 1/8.25
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.byte $15,$15,$16,$16,$17,$17,$18,$18,$19,$1A,$1A,$1B,$1C,$1D,$1E,$1F
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; 1/8.0 - 1/4.25
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.byte $20,$21,$22,$23,$24,$25,$27,$28,$2A,$2C,$2E,$30,$33,$35,$38,$3C
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; 1/4.0 - 1/0.25
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.byte $40,$44,$49,$4E,$55,$5D,$66,$71,$80,$92,$AA,$CC,$00,$55,$00,$00
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