Gravity is a simple gravity simulator. It can either perform a simulation, which can be very slow, or it can play an existing simulation in normal speed. In the simulated universe there are only about 1000 particles and only the force of gravity. This means that there will be no star formation or even collisions between particles. Since this is a simple gravity simulator light will not bend, so there will be no gravitational lensing. No worries though, I'm planning on doing a black hole simulator in the future. In this gravity simulator, however, one can see some spectacular motion of the particles, and if the viewing angle isn't good enough one can always rotate the universe with the arrow keys.