It's "Geometry Wars" meets "Amorphous+".
With some RPG elements added. The music was good, but with only one track it got kind of stale by the time I achieved "Defender of Pixela-RT". Also, a possible improvement an (unlockable) option like Amorphous+'s Hardcore Mode, where you encounter every type of enemy right from the start.
For those having trouble getting the high chain trophies, (make sure you have all bronze and silver trophies so you can upgrade these right away,) focus on fire rate, but put at least one point into spread. Move as little as possible, except to pick up a shield. By minimizing pixel pickup, you'll eventually destroy 500-1000 enemies without the difficulty rising to the point where it's impossible to not get hit at least once.