Absolutely amazing game. My first Metroid title and I really enjoyed it. The puzzles and map design kept me guessing the whole way through. I think the only aspect I didn't really like were the boss fights. They were so good but honestly I prefer a health bar and I'm too jazzed about the shooter combat. Surprinsingly ai didn't even really mind that the bosses could take a while to defeat as the difficulty curve felt about right.
My only other niggle is some of the speed booster puzzles, they requure incredibly precise inputs and good reflexes which can make them frustrating!!