SCREEN 13
RANDOMIZE TIMER

REM CONSTANTS AND DIMENSIONS
DIM P(4, 150, 2)
PI = 3.141592654#
CX = 160
CY = 100
RM = 90
isStart = 0

4990 REM ART FORM 1
5000 N = INT(RND(1) * 4 + 3)
5010 AN = PI / N
5020 R = (RND(1) * .2 + .3) * RM: RR = 100
5030 M = INT(RND(1) * 30 / N + 10)
5040 IY = R / M
5050 IX = (RR - R) * TAN(AN) / M
5060 REM DEFINE BASIC CURVE
5070 FOR i = 0 TO M: P(0, i, 1) = 0: P(0, i, 2) = i * IY: NEXT i
5080 P(2, 0, 1) = 0: P(2, 0, 2) = 0: P(2, 1, 1) = 0: P(2, 1, 2) = IY
5090 FOR i = 2 TO M + 10
5100 B1 = (i - 1) * IY
5110 B2 = i * IY
5120 M1 = (RR - B1) / ((i - 1) * IX)
5130 M2 = (RR - B2) / (i * IX)
5140 P(2, i, 1) = (B2 - B1) / (M1 - M2)
5150 P(2, i, 2) = P(2, i, 1) * M1 + B1
5170 NEXT i
5180 REM ROTATE AND TRANSLATE BASIC CURVE
5190 CA = COS(AN - PI): SA = SIN(AN - PI)
5200 FOR i = 0 TO M + 10
5210 X = P(2, i, 1) * CA - P(2, i, 2) * SA
5220 Y = P(2, i, 1) * SA + P(2, i, 2) * CA + RM
5230 P(2, i, 1) = X: P(2, i, 2) = Y
5250 NEXT i
5260 REM CALCULATE END POINTS
5270 P(1, 0, 1) = 0: P(1, 0, 2) = RM
5280 FOR i = 1 TO M
5290 B1 = i * IY: M1 = (RR - B1) / (i * IX)
5300 FOR J = 1 TO M + 10
5310 IF P(2, J, 1) = P(2, J - 1, 1) THEN M2 = 9999: GOTO 5330
5320 M2 = (P(2, J, 2) - P(2, J - 1, 2)) / (P(2, J, 1) - P(2, J - 1, 1))
5330 X = (P(2, J - 1, 2) - P(2, J - 1, 1) * M2 - B1) / (M1 - M2)
5340 IF X < P(2, J - 1, 1) OR X >= P(2, J, 1) GOTO 5380
5350 P(1, i, 1) = X
5360 P(1, i, 2) = M1 * X + B1
5370 GOTO 5400
5380 NEXT J
5400 NEXT i
5410 GOSUB chooseColor
5420 REM GRAPH ROUTINE
5430 FOR i = 0 TO N - 1
5440 CA = COS(2 * i * AN): SA = SIN(2 * i * AN)
5450 X = 0: Y = 0
5460 GOSUB 5550
5470 NEXT i
5480 FOR i = 0 TO N - 1
5490 CA = COS(2 * i * AN + AN + PI): SA = SIN(2 * i * AN + AN + PI)
5500 X = -RM * SIN(2 * i * AN + AN): Y = RM * COS(2 * i * AN + AN)
5510 GOSUB 5550
5520 NEXT i
5530 FOR i = 1 TO 100: GOSUB Pause: NEXT i
GOTO 4990
5540 REM LINE ROTATE, TRANSLATE, AND PLOT ROUTINE
5550 PSET (CX + X + P(1, 0, 1) * CA - P(1, 0, 2) * SA, CY - Y - P(1, 0, 1) * SA - P(1, 0, 2) * CA): GOSUB Pause
5560 LINE -(CX + X + P(0, 0, 1) * CA - P(0, 0, 2) * SA, CY - Y - P(0, 0, 1) * SA - P(0, 0, 2) * CA): GOSUB Pause
5570 FOR J = 1 TO M
5580 PSET (CX + X + P(1, J, 1) * CA - P(1, J, 2) * SA, CY - Y - P(1, J, 1) * SA - P(1, J, 2) * CA): GOSUB Pause
5590 LINE -(CX + X + P(0, J, 1) * CA - P(0, J, 2) * SA, CY - Y - P(0, J, 1) * SA - P(0, J, 2) * CA): GOSUB Pause
5600 LINE -(CX + X - P(1, J, 1) * CA - P(1, J, 2) * SA, CY - Y + P(1, J, 1) * SA - P(1, J, 2) * CA): GOSUB Pause
5620 NEXT J
5630 RETURN

Pause:
FOR j1 = 1 TO 10000
    IF INKEY$ <> "" THEN
        GOTO endProgram
    END IF
NEXT
RETURN

chooseColor:
IF RND - .5 > 0 THEN
    COLOR 7
ELSE
    IF RND - .5 > 0 OR isStart = 0 THEN
        COLOR 4
    ELSE
        COLOR 0
    END IF
END IF
'CLS
isStart = 1
RETURN

endProgram:
COLOR 7
END

' TODO:
'  remove linenumbers
'  more colors