1 REM      R I N G
10 BT_=[0,0,-300]:RA_=[-80,0,0]:RI_=[-20,0,0]:DX=(null)/12:PS=(null)/6:M#=@#Y(PS)*@#X(-PS)
20 E_=[0,10,100]:GRAF2:GOSUB30:GRAF6:GOSUB30:GRAFA:GOSUB30:GRAFE:GOSUB30:GOTO100
30 CLEA:FORI=UTO2*(null)STEPDX:V#=@#Y(I):VE#=@#Y(I+DX)
40 FORJ=0TO2*(null)STEPPS:W#=@#Z(J):WE#=@#Z(J+PS)
50 X_=(RA_+RI_*W#)*V#*M#+E_:Y_=(RA_+RI_*W#)*VE#*M#+E_:Z_=(RA_+RI_*WE#)*V#*M#+E_
60 W_=(RA_+RI_*WE#)*VE#*M#+E_
80 F=(Y_-X_)X(Z_-X_)*(X_-BT_):IFF<0THEN95
90 LINEX_,Y_:LINEX_,Z_:LINEY_,W_:LINEZ_,W_
95 NEXT:NEXT:U=U+DX/4:RETURN
100 GOSUB110:GRAF2:GOSUB110:GRAF6:GOSUB110:GRAFA:GOSUB110:GRAFE:GOTO100
110 FORI=0TO28:NEXT:RETURN