SET WINDOW -1,1,-1,1
LET s=SQR(3)
FOR d=0 TO 8
   DRAW a(d) WITH SCALE(1/3^d,1/3^d)*SHIFT(-0.5,s/6)
   DRAW a(d) WITH SCALE(1/3^d,1/3^d)*SHIFT(-0.5,s/6)*ROTATE(2*PI/3)
   DRAW a(d) WITH SCALE(1/3^d,1/3^d)*SHIFT(-0.5,s/6)*ROTATE(4*PI/3)
   gsave STR$(d)&".gif"
   CLEAR
NEXT d
END
EXTERNAL PICTURE a(d)
LET a=0
PLOT LINES:0,0;
LET x=1
LET y=0
PLOT LINES:x,y;
FOR k=1 TO 4^d
   LET s=k
   DO
      LET s=s/2
      IF NOT(s=INT(s)) THEN EXIT DO
      LET t=t+1
   LOOP
   IF t/2=INT(t/2) THEN
      LET a=a+PI/3
   ELSE
      LET a=a-2*PI/3
   END IF
   LET t=0
   LET x=x+COS(a)
   LET y=y+SIN(a)
   PLOT LINES:x,y;
NEXT k
END PICTURE