game · 3 min
Spacetime
A gravity sandbox. Drop a probe and thread a stable orbit, swap Earth for a neutron star and watch the grid cave in, then fling two black holes together and feel the gravitational waves. Real surface-gravity and escape-velocity numbers; the same inverse-square pull as the rest of this site, finally with a control panel.
Mass tells spacetime how to curve; spacetime tells matter how to move. This is that sentence, made playable.
Pick a body and the grid behind it caves in to match its mass, from the Moon’s gentle dimple to a black hole’s bottomless funnel. The numbers on the panel are real: surface gravity in m/s², escape velocity in km/s. The sandbox itself is a stylized model, tuned so you can actually fly in it.
Drag from the probe to set a launch vector, then try to find a stable orbit. Too slow and you fall in; too fast and you sail past escape velocity and off the chart. Then hit “merge” and two black holes spiral together and ring spacetime like a bell, which is exactly what LIGO heard in 2015.
Best orbit time is saved to localStorage. Single HTML file, no dependencies.