Sat 30 Dec 2006
With the pencil tool, draw a line from top left toward bottom right. Note that the lines you draw have direction (lines drawn from left to right act as the floor and lines drawn from right to left act as the ceiling).
Use the hand tool to move the drawing area (you can also hold down the space key while using the pencil tool to get the same effect.).
After you finish drawing, press the play button.