At first glance, Sentinel Returns is totally baffling. If you just pop in the CD and start playing, you'll be convinced that the code itself is somehow broken. You can't move. All you can do is cause giant metallic pylons and cubic fleshy dirt clumps to appear and disappear. And you can look around. That's it. Just what the heck is going on here? One of the most riveting puzzle games in recent memory, that's what.
Early observations are correct, however. You actually can't move. Not in the traditional sense at least. Instead, you create robot hosts that look like statues with disembodied, featureless heads. You "move" by transferring your sentience into it. Huh?
Here's the scoop: You exist on an alien landscape draped in perpetual night. Watching from the highest point in the landscape is a being called the Sentinel. He is part fleshy colossus, part abstract sculpture, and part gun tower. He is your enemy. He is continually scanning the landscape, looking for you. When he finds you, he locks his gaze on you and begins absorbing your energy.
Everything in this world is based on energy and elevation. You can create or destroy objects if and only if you are above them - hence the Sentinel has a terrific advantage. You begin each level on the lowest plane in the level, with a handful of energy. You use the energy to create boulders and robot hosts and begin your climb. Your goal is to attain an elevation higher than the Sentinel's and absorb him. The basic trick is to create a stack of boulders, with a robot host on top. Then teleport into the host. From there, you should be able to create a single host (no boulders) on a plane higher than the one you started on. You then reabsorb your old boulders and host. You now have the same amount of energy as when you started, but you're on a higher plane. Closer to the Sentinel. And easier for him to see.
You can also create trees to block his gaze. More importantly, a fair number of them are scattered throughout each level, and they can be absorbed for their energy - as long as you're higher than they are. So, climbing serves another purpose as well, to unlock potential energy resources.