I give to you a frictionless vacuum with perfectly elastic collisions! All the rectangles are draggable. The moving circle is also draggable, but it's harder to catch. If you want to delete a rectangle, move your mouse-pointer to touch it and press X. The moving circle cannot be deleted. To add a diagonal up-to-down rectangle, press 1. To add a diagonal down-to-up rectangle, press 2. To add a vertical rectangle, press 3. To add a horizontal rectangle, press 4. If you can't remember or refuse to remember the numbers, you can also copy and paste existing rectangles. To do this, hold your mouse-pointer over any rectangle, then press C to copy it. At any time from that point on, you can press V to paste the rectangle. To change the copied rectangle, repeat the copying process. When a new rectangle is created, it appears at the mouse-pointer.
