In this display the space has dimensions of x along the horizontal axis and pe along the vertical axis. The function pe(x) is shown in green. The object in this case is just a 1kg ball. You may position the ball by clicking the mouse button. An initial velocity either plus or minus may be entered in the ix' data entry box. Clicking the Action button starts time flowing. If you give the object too much velocity, it will spend a lot of time off screen. Velocities in the 0.5 m/s range work OK.
There are two views of the object in this display. The object as observed in normal space is shown in red. It simply moves back and forth like the block in the block and spring arrangement. If we could make observations in a space that included a potential energy dimension we would see movement like the cyan object. Making the potential energy visible helps us understand why the object moves back and forth. You might imagine the cyan object threaded on a wire in the shape of the potential energy curve and subject to the force of gravity oriented down the screen. That would produce exactly the motion you see here.