Phantasy Star Online but with Gundam
it's not the most complicated game but as far as the fun factor goes, this is one of the most fun and simple games around. The game plays kind of like Phantasy Star Online, where you enter levels and have to clear them, usually just getting to the end and fighting boss suits, which are almost always the main Gundam or the villain of a series.
And you can get parts and make your own custom suits based on parts from actual suits and while there are limitations on what you can build, you can pretty much make what you want with the parts given to you. Want to make a Zaku II with parts of Turn A? Want to splice the classic Nu with Hi-Nu? Just want to recreate your favorite suit and use it? You can. You can even do some of the signature attacks like the God Finger.
Game also has multiplayer and it's fun.
Good game, worth buying.