Beat Hazard is a game best described as " Geometry Wars meets Audiosurf". Both of those games are great, so it is not without reason that Beat Hazard is great as well.
Either with a gamepad or mouse and keyboard, you control a spaceship with only one objective: shoot everything that moves. The game floods the screen with hostile spaceships, asteroids and a boss here and there while you concentrate on avoiding enemy fire and grabbing power-ups. The power-ups consist of score multipliers, weapon upgrades, bombs and volume upgrades. The volume upgrades does nothing other than increasing the volume of the song, which is kind of weird since you really want to be able to hear the song fully all the time. You start with 3 lives in each song and have no ability to gain more. Once you collide with an object or get hit by incoming fire, you lose a life and respawn.

The bosses spawn when there is a big rhythmic change in the song. They slowly enter the screen from any of the sides and starts firing their several weapons. While the boss battle is on, no other enemies enters the screen for some time, which grants you enough time to focus on bringing it down. I found that the most effective strategy against them is circle-strafing while focusing my fire on the boss' weapons. The boss battles is a neat addition to the gameplay and keeps the game from getting too repetitive.

The first you see when you start a game is a warning for people with light sensitivity, and that is not without reason. The game can easily turn your screen into a mess of different colours that all flash and change in time with the music. This greatly enhances the experience of playing the game, however, it can sometimes become too much. When your spaceship is fully powered up and you're at a furiously fast part in a song, your shots can easily cover half of the screen which makes it kind of hard to avoid colliding into smaller objects. This only really becomes a problem when you die, since the game automatically respawns you in the middle of the screen without any indication of where you are. This can often lead to a frustrating death-streak which often means Game Over.

In short: This game is great and you should at least consider trying it.
The game is currently available on Steam for $9.95 or €6.99 and as an Xbox Live Indie game for 400 MS Points.