Bohrdom

This is an atomic fighting game loosely based on a chemistry model that is itself loosely based on reality. It features constant nuclear combat and radiation everywhere. Technically. If you love chemistry or physics, you'll probably enjoy this. If you hate chemistry or physics... you'll also probably enjoy this.

Play as an electron and cause havoc on your road to freedom, or play as nucleus and struggle to control a full atom's worth of particles.
In terms of content, this game comes with a short campaign, single-player challenge modes, and split-screen multiplayer that allows for 2-4 players.
There's also online multiplayer in the form of the Quantum Nightmare modes. Quite possibly the hardest online multiplayer you'll ever encounter. It's not recommended to take it too seriously.