The Sentinel is a 3D puzzle game created by Geoff Crammond.
The game takes place on a 3D gridded landscape featuring different elevation levels . The Sentinel is sitting on the highest point and the player's goal is to absorb it by teleporting to its square.
The player moves by creating a new body on a visible square and transferring her consciousness to it. She can also create rocks to gain altitude and get a better view of her surroundings. Creating items and bodies cost energy, which can be regained by absorbing other items on the terrain (trees, rocks, bodies...). The Sentinel rotates periodically, and if it sees the player it starts absorbing her energy, eventually killing her if she doesn't escape the Sentinel gaze in time.
The game features 10000 levels unlockable by codes. Completing a level with more energy left gives access to higher levels than completing the level with almost no energy.
After the first few levels new elements are added to the game, like Sentries (extra Sentinels) that can transform trees near the player into Meanies, a creature that can teleport the player to a random location of the board.