Worldsmith

Worldsmith is a sandbox of planetary dials. Choose a map from the menu, from bare rocky worlds to full stars, then turn the four controls that decide what happens next: Temperature, Pressure, Gravity, and Volatiles.

Every dial has a range and every combination lands somewhere. Nudge a warm world into the habitable band and liquid water appears, the sky becomes breathable, and life takes hold. Push a star past its limit and it goes supernova, or collapses into a black hole.

The readout keeps score while you work: 271 K, 1.37 atm, 1.14 g, 55 percent volatiles, mass 0.96 Earths, and a counter of the 17 discoveries still to find on Terra Nova.

No timers, no fail states. Just you, a globe, four dials, and whatever they cause.