The goal of Magnetis is to connect magnets facing opposite directions together. When you do, they contract and everything in between disappears.
You get more point for longer lines, and even more points for chained reactions, so you're encouraged to plan your moves ahead. Up to 4 players can play in split screen. There are many game modes, like Normal, Time Attack, Block Attack, Battle, Cooperative, and players can even team up (for instance, if you have buddy who's really strong, you can play at 3 against 1). It might not seem like it at first, but there can be quite a bit of strategy involved in planning ahead for your combos.