WINDOW removes the boundaries from the turtle's field of movement. If the turtle moves beyond the borders of the graphics window, it continues to move, but cannot be seen. The graphics window becomes a small window overlooking the plane on which the turtle can travel.
The range of movement for the turtle when WINDOW is in use is -32,768 to 32,767.
? RT 45 FD 1000
The turtle has moved off the window.