Imagine you have a little robot that holds a pencil. Set it down on a sheet of paper and give it these instructions:

Move forward 3 units and turn right. Move forward 1 unit and turn right. Move forward 2 units and turn left. Move forward 1 unit and turn left. Move forward 2 units and turn right. Repeat.

If the robot makes its turns at 90° angles, it will produce this figure:

But, remarkably, if it turns at 120° it will draw this: