Since I wouldn't want to disappoint LoneSage...
Chaos Field is a bit weird. I really like what MileStone were trying to accomplish with the game (chaining bullets, environmental shifting), but it just seems that the ideas didn't work very well together.
The whole system revolves around intelligent use of the two environmental polarities: Order Field and Chaos Field (so this a bit like ESPGaluda's Kakusei system in that you're changing the entire environment and how enemies react). Also worth noting is that every time you shift you're invincible for a couple of seconds. In Order Field, destroying enemy targets nets you loads of Meta Cubes (for each 10 collected, you are granted a Special Weapon usage, of which 10 total can be stored at any one time), but fewer shots are fired at you (chaining bullets and target destruction is what raises your multiplier). In Chaos Field, the opposite applies.. destroyed targets release fewer Meta Cubes but the number of projectiles increases significantly. Between bosses your multiplier is paused (it's on a timer much like in Dodonpachi, the horizontal yellow bar in the upper right of the screen is the timer.. which has at max, a 5 second interval). Because of the pauses between bosses, it's possible to chain an entire stage.
So the gist here is, start in Order Field, build up your Special Weapon stock (the Wing Layer and the Lock-On Web are the two Special Weapons) while doing some basic chaining and then switch into Chaos Field to abuse the crap out of your special weapons. Wash, rinse, repeat. The biggest problem I have is that it's wall-to-wall boss milking... however, with the time-based bullet chaining, it makes more sense for the game to be a boss rush. Also, the closer the stage boss timer is to zero when killed (without going below that), the higher the end-stage bonus. Again, a weird system and I would
strongly recommend watching at least the level 1 replay by VTF-INO (hosted on
www.super-play.co.uk) just to get a clear idea of how the system works and should be used.
As stated, the soundtrack is definitely worth picking up.
When it comes to MileStone's stuff, I'd prefer to play Radirgy and Karous (I haven't had a chance to try out IllVelo yet). Both games are far more kinetic and feature a more traditional level layout (they're very much in line with Takumi's games).