Shadow Complex follows Jason Fleming, an everyman who heads off for a day of spelunking with a girl, Claire, he met in a bar a few nights previously. As fate would have it, the cave houses a secret militia compound run by a group looking to start the next civil war. Claire is kidnapped, Jason finds a kick-ass power suit and the race is on to stop the militia's plans. Though the story runs concurrent to Orson Scott Card's Empire, reading the novel beforehand isn't necessary.
Gameplay follows Metroid's play pattern right down to the missiles and red doors. Again, this is by no means a bad thing as the setup works and provides a lot of play (and replay) for its 1200 MS Point price tag. My first run-through lasted nearly 12 hours, which is a pretty good chunk of time considering the length of some retail games. The structure and Achievements support multiple run-throughs as well. You can go for a 100% completion on items, or attempt a speed run with a minimum number of items.
For players unfamiliar with Metroid, everything in Shadow Complex is interconnected. You start out in a small area, but as you unlock new items and components for your Omega Suit, you'll open up new paths and larger portions of the map. Upgrades include simple things, like a climbing harness (wall jump ability) as well as more complex items like a hook shot (grappling hook) and jetpack (short range flight). Discovering the interplay between these abilities is half the fun. For instance, you can start a super run and then use the jetpack to keep momentum going. Or, you can use the foam grenade on a wall, then launch a grenade into the goop, creating a sticky bomb.
Outside the main campaign, Shadow Complex offers up three challenge modes dubbed Proving Grounds. These areas aren't much different than the VR mode in Bionic Commando: Rearmed and really push your abilities with the game's items. This is the one area I've yet to really get a handle on. Challenges start out easy but get really complicated as you push through. Completing all three modes earns an Achievement and a spot on the Leaderboard, but also teaches you some neat, creative ways to combine item abilities.
Another neat "brag item" is the real time stat tracker. You can compare your score and stats with friends and other players via the Leaderboard, or watch an in-game indicator. As you rack up specific stats like melee kills and headshots, a small indicator will pop-up and let you know how you compare to a friend. It doesn't matter much in the long run, but I'd be lying if I told you a friend and I didn't get a little competitive over in-game stats.