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This lets you pilot a ship around and into the horizon of Schwarzschild black hole. (Click inside if it doesn't respond to you.) The arrow keys fire the rocket engines. Enter resets the ship. You get one point every time you catch the orbiting moon. Everything is from the point of view of the proper time on the ship itself; the "heartbeat" happens once per second with respect to the ship's proper time. From the point of view of the ship, the horizon is locally smooth and so is not shown by default; press "h" to toggle it. Of course if you happen to cross the horizon you can't come out again and end up hitting the singularity rather quickly. The fluctuations of the shape of the ship measure the local tidal forces.
Compare with the view from outside .