Pipedown is great 3D puzzle solving fun where you arrange the pipes to allow the ball to drop through to the bottom.

Arrange the pipes so that the ball will be dropped from the top down to the bottom through the pipes. Once ready, click the Drop button to activate the ball drop.

Use the following controls:
Mouse: Click and drag mouse to change your viewpoint.
Mouse Button: Click on a pipe then click an arrow to move the pipe in that direction.