mirror of
https://github.com/mauiaaron/apple2.git
synced 2024-06-26 00:29:27 +00:00
43 lines
1.3 KiB
QBasic
43 lines
1.3 KiB
QBasic
10 REM
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20 REM LORES80 CONCENTRIC CIRCLES
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30 REM
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40 REM BY JIM SATHER --- 6/21/84
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50 REM
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70 REM
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80 REM FOR EMULATOR : DEADC0DE.ORG/apple2
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90 REM
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110 REM
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120 REM INITIALIZE
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130 REM
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140 STR80 = -16383 : COL80 = -16371 : NOMIX = -16302 : MBD = -16300
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150 AUX = -16299 : FRCTXT = -16290 : LCLEER = -1998 : CLR = 48
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170 GR : POKE STR80,0 : POKE NOMIX,0 : POKE COL80,0 : POKE FRCTXT,0
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180 POKE AUX,0 : CALL LCLEER : POKE MBD,0 : CALL LCLEER : REM CLEAR SCREEN
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200 REM
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210 REM COLOR / CIRCLE COMPUTATIONS
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220 REM
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230 PTS = 208 : REM NUMBER OF ANGLES SAMPLED
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240 FOR ANGLE = 0 TO PTS-1
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250 A1 = 6.2831852 * ANGLE / PTS : SI = SIN(A1) : CO = COS(A1)
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260 FOR C = 0 TO 7 : COLOR = C : IF ANGLE > PTS/2 THEN COLOR = C+8
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270 IF C = 0 THEN COLOR = 15
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280 R = 24 - C*3 : V = 24 - SI * R : H = 40 + CO * R * 1.36 : GOSUB 330
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290 NEXT C : NEXT ANGLE
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295 POKE 7987,255
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300 GOTO 300
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320 REM
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330 REM PLOT H,V (H = 0-79, V = 0-47)
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340 REM
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350 H2 = INT(H) / 2
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360 IF H2 - INT(H2) THEN POKE MBD,0 : PLOT H2,V : GOTO 400
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370 POKE AUX,0 : CSAV = PEEK(CLR) : C2 = CSAV / 2 : C2% = C2
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380 IF C2 - C2% THEN C2% = C2% + 128
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390 POKE CLR,C2% : PLOT H2,V : POKE CLR,CSAV
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400 RETURN
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