I found the battle system to be very daunting. It's a continuous puzzle that isn't very engaging. After a few hours it just becomes a chore, and takes alot of the fun out of the game. When you have boss battles they reverse the combat system and throw in all types of special rules. This helps to break up the mundane system, but also adds a layer of confusion since its backwards from all normal battles.
The bosses were just randomly thrown in, you explore a level, get 1 or 2 hints about them, battle and they are done. The lack of any type of experience or advancement is a huge disappointment. You can buy or earn better equipment, but it breaks over time and has to be replaced.
It was a good way to pass some time, but not something I see myself ever playing again.