A Metroid game engine? I appreciate it, but I made my own...
GM just doesn't work on my comp right now. Half the fun of having GM is making stuff yourself.
I had the game set up like, say Metroid Fusion for example, but had more of a custom Metroid Prime HUD complete with an expandable ammo tank for weapons, missile reserves, you name it. All of which could be expanded with expansions. I also had five beams, the space jump, morph ball, directional shooting, morph ball bombs, bomb jumping, and a new toy I made called the Gravity ball that let Samus float over gaps while in Morph ball mode.
Things were working pretty good, her space jump was the only issue I needed to fix, really. Oh, I also had charge beams. No beam combos yet though 8<