The later Ambrosia titles of the Escape Velocity series are based on very similar game mechanics that build on those of Maelstrom.
In 40 levels on a two-dimensional playing field with cyclic boundary conditions (projection of a two-dimensional torus) the player navigates a spacecraft that he can turn and accelerate forwards. Unlike the precursor Asteroids the player's ship keeps drifting at its given speed.
Beside other elements of the game there are asteroids drifting in random straight lines (repeatedly) over the playing field, that mus all be destroyed in order to complete the stage (“wave”). At the beginning of a stage the own ship gets placed head-up into the center of the playing field, while an amount of big asteroids gets launched on the playing field from the edges. During the first 30 seconds of each stage other elements may appear randomly.
The capabilities of the own ship can be expanded through collected extras. They are lost with the destruction of the ship. A force shield protects the player's ship for a few seconds after it is spawned and may be activated until the limited amount of energy is exhausted.