; butterfly 
; By michael mitchell
; 01/20/85

PROC DEMO2()
CARD A,B,C,D,X,Y,J,K,COL,I,Q
  Graphics(11)

  Poke(710,0)
  Color=00
  A=1 B=1 C=1 D=1
  X=Rand(70)+1
  Y=Rand(190)+1
  J=Rand(50)+1
  K=Rand(190)+1

  For I=1 TO 9400 
  DO
    Plot(X,Y) 
    Drawto(J,K)
    Plot(J,Y) 
    Drawto(X,K)
    X==+A 
    Y==+B 
    J==+C 
    K==+D 

    Q=Rand(50)
    IF Q>40 THEN  
      COL==+1  
    FI  
    IF COL>14 THEN 
      COL=1 
    FI

    COLOR=COL

    IF X>=79 THEN A=-A X==+A  FI
    IF J>=79 THEN C=-C J==+C FI
    IF J<=0 THEN C=-C J==+C FI
    IF X<=0 THEN A=-A X==+A FI
    IF Y>=191 THEN B=-B Y==+B  FI
    IF K>=191 THEN D=-D K==+D  FI
    IF K<=0 THEN D=-D K==+D  FI
    IF Y<=0 THEN B=-B Y==+B FI

  OD
RETURN