10 HOME : FOR V = 1 TO 15: GR :T = RND(9):S% = RND(9) *18 +1: FOR Y = 0 TO 19: FOR X = Y TO 19: GOSUB 20: PLOT X,39 -Y: PLOT 39 -X,39 -Y: PLOT 39 -X,Y: PLOT X,Y: PLOT Y,X: PLOT 39 -Y,X: PLOT 39 -Y,39 -X: PLOT Y,39 -X: NEXT X,Y: FOR D = 1 TO 2E4: NEXT : NEXT : RUN