Milky Way is a PC sandbox game. It allows you to conduct astrophysical simulations to indulge your curiosity. This game incorporates real observational data and accurate theoretical models to predict various phenomena such as planetary collision, relativistic and quantum effects around a black hole.
According to IndieDB, it is currently ranked at 36 among 32,381 other games. A playable demo is available at http://www.scixp.com.