Beat Hazard's level generation is based on the same sort of generation that Audiosurf is. The game detects the length of the song, basic beats, and progression, and builds a level to fit the song. The same song will always give the same level, so once you have played it once, you know what is coming. Besides using the song to determine the level, Beat Hazard also uses it to determine the power of your shots. The slower the tempo and the quieter the song, the less bullets you will fire. Conversely, unlike Audiosurf, this makes the slow songs in Beat Hazard incredibly tough while the fast songs are fairly easy. The enemy creation is not scaled as much as your bullets are. Go figure.
There are not that many enemy types in Beat Hazard, unfortunately. Most of the game revolves around either fighters, asteroids, or bosses. Fighters generally come in from the side of the screen and move in and out in a predetermined (and hypnotic) pattern. Asteroids float around as asteroids do, looping from one side to the other. Bosses are massive ships that have more than a single weapon system on them. There are a number of different weapons that can be used by the enemies, such as homing mines or torpedoes, but you can only use your standard shot and bombs. You upgrade this by gathering volume and power upgrades, but really, it doesn't matter that much. The only thing that matters is how fast and loud the music is.
Beat Hazard's strengths lie primarily in engaging the player and the visualizations. For example, when you are playing a song and it goes suddenly acapella, your stomach drops as you realize that you have no more shot power. Then, when the song resumes with a sharp start and the screen explodes in a cataclysm of color and light, you feel like a diety handing down punishment to the lesser beings. On some of the fastest songs, your shots can literally wipe out an entire screen without blinking. It's quite impressive. The game also incorporates synchronization with the song better than Audiosurf, thanks to the tying of the shots into the song itself. Where Audiosurf blocks are roughly correlated to the song, Beat Hazard is directly influenced by what you play inside it.
Likewise, there are a number of major cons. The main one is that the game is lacking in content. The leaderboards are not separated by song, which means that one song always dominates a particular leaderboard. Enemies are mostly the same, only with different ways of attack. There are only two boss types: small and large, and there's no difference in how you fight them. The only difference is in the amount of punishment they take. There's two game modes, which miss some of the essentials. For example, you can't load a playlist and play it. You can only play individual songs or entire folders. The game is also missing the album completion feature of the original, console incarnation, where the player can tell how much of an album he has completed and get bonuses for clearing it.
There's also the concern that many people can't deal with the chaos going on when they play. There is now a low-intensity option, thanks to patches by the developer, but it's still a very visually intense game. Lots of pulsating, explosions, and other crazy nonsense. It can be hard to play, especially for those not accustomed to the chaos of arena shooters, and even experienced gamers will be challenged by the overload of the senses that the game pushes. While we enjoy this, it's certainly not for everyone. There's also the detriment that the game requires you to have an overload to play it at all, since soft, slow songs are disadvantaged compared to fast songs. There needs to be a system in place to help circumvent that.
Since release, Beat Hazard has received a number of patches which address player concerns. Just today a patch was added to the game that enables custom preference files, adds iTunes support (through a DLC, thanks to licensing fees), and the much-awaited 2-player modes. Other patches have added the Chill Out mode, which acts like a playable visualiser (similar to the Audiosurf background mode), and support for formats besides MP3, such as FLAC or OGG. The developer is also heavily active in the game's Steam forums and listens to the player base, which makes him much, much better than your averag emainstream developer. After all, he is listening!
Beat Hazard is a flawed game, but a great one nonetheless. The developer realizes the potential and through his updates just keeps making it better and better. Potential future plans include challenges (such as the skulls in Halo), support for more audio types, online multiplayer, and leaderboards separated by song. Thanks to its low price, we can heartily recommend Beat Hazard to everyone that isn't suffering from photosensitive epilepsy. It's cheap, has a lot of replayability, is obviously inspired by arcade classics, and just plain fun to play. It's one of the best indie games on Steam, in its price bracket or otherwise.