This is a bunch of discs that do inelastic collisions. Gravity pulls them down but the piston in the floor tosses them up. What do you expect to be the long time behavior of the simulation? Figure it out or … relax and observe. :)

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Here is the full story. (Spoiler alert!) The code is a MD simulation with soft core discs. Right click (or shift click) opens controls for a few selected parameters.