10 REM TWISTER-DEMO
20 HGR2
30 FOR A2 = -180 TO 180 STEP 4
40 A3 = 2.4+SIN(COS(A2*0.0174533))*1.2
50 AN = -3.141593+SIN(A2*0.0174533)*3.141593
60 FOR Y = 0 TO 191 STEP 2
62 AM = A3 * (1.5+SIN(3.141593*Y/191+1.570796))
65 FV = AM+AN
70 X1 = 35*SIN(FV)
80 X2 = 35*SIN(FV+1.570796)
95 X3 = -X1
105 X4 = -X2
108 HCOLOR = 0: HPLOT 105,Y TO 175,Y
110 IF X1 < X2 THEN HCOLOR = 1: HPLOT 140+X1,Y TO 140+X2,Y: GOTO 130
120 IF X3 < X4 THEN HCOLOR = 1: HPLOT 140+X3,Y TO 140+X4,Y
130 IF X2 < X3 THEN HCOLOR = 2: HPLOT 140+X2,Y TO 140+X3,Y: GOTO 150
140 IF X4 < X1 THEN HCOLOR = 2: HPLOT 140+X4,Y TO 140+X1,Y
150 NEXT Y
160 NEXT A2
170 GOTO 30