Probably my favorite 2D Metroid, but I'm not sure I've ever completed another one so I don't know how much that really says. The exploration feels really good, and the movement puzzles are a canny way to avoid making exploration purely about "shoot every suspicious wall." The boss fights on the other hand are an awful mess of "guess my gimmick" and quick-time events. If you really want a great Metroid-like, play Environmental Station Alpha.