1 REM        L  O  C  H
5 PS=(null)/8:KZ_=[0,7,0]:Q=1.1
10 BT_=[0,0,-300]:RA_=[-68,0,0]:RI_=[0,120,0]:DX=(null)/18:H=4:DH=.2:M#=@#X(PS)
20 E_=[0,99,60]:GRAF2:GOSUB30:GRAF6:GOSUB30:GRAFA:GOSUB30:GRAFE:GOSUB30:GOTO100
30 CLEA:FORI=UTO2*(null)STEPDX:V#=@#Y(I):VE#=@#Y(I+DX):G=8*DH
40 FORJ=QTOHSTEPDH:A_=RA_*J:B_=RI_*G/J:BE_=RI_*G/(J+DH):AE_=RA_*(J+DH)
50 X_=(A_-B_)*V#*M#+E_:Y_=(A_-B_)*VE#*M#+E_:Z_=(AE_-BE_)*V#*M#+E_
60 W_=(AE_-BE_)*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:Q=Q-DH/4:U=U+DX/4:RETURN
100 GOSUB111:GRAF2:GOSUB110:GRAF6:GOSUB110:GRAFA:GOSUB110:GRAFE:GOTO100
110 FORI=0TO26:NEXT:RETURN
111 FORI=0TO22:NEXT:RETURN