You play as Zizou and upgrade your speed and shots with a Gradius style install bar. There is a shop with a lot of upgrades you can buy with the games' currency, Tres. Such as life, more attack power and magic abilities that can be used once per stage.
There are four difficulty settings, which vary from easy to very hard. Upon beating the game, you unlock several things, such as a new character, mini games such as poker and a rhythm game. There is also a museum you can use, playing levels which are achievements, and bonuses for your next new game.
All of these things make it an excellent game and my new favourite series. The first game was pretty good as well. It can be very addicting, so beware! I am really happy with this one!