In Balder2D, players control small probes which shoot tiny projectiles with which they try to destroy each other. It features a 2D overhead view of the playing field. Probes may be human or computer controlled.

A probe can perform the following actions:

* rotate
* fire projectiles
* "stick" to a wall
* push off of a wall
Players may rotate their probes while in flight, but the only way to change the direction or speed of flight is by firing projectiles (which gives a small kick in the opposite direction) or by running into walls or other probes.