A very simple indie multiplayer simultaneous turn-based base shooting game, if that description makes any sense.
It's a space-version of the age-old "shoot the other player's cannon" game where players took turns choosing fire velocity and angle, trying to fire a cannon ball that, when affected by gravity and wind, would hit the other player's cannon. (This game eventually evolved into "Worms").
In Gravitas, players are a small ship in a randomized cluster of planets and fire shots trying to hit the other ships. The shots are naturally affected by the planet's gravities, which sometimes created hilarious shots.