Requires solving spatial and physics based puzzles using portals
The main mechanic of the game revolves around solving different puzzles using a handheld portal device - a device that can bend space and time to create a wormhole through which you can move.
Throughout both Portal games there are hints left in various forms that fill in more of the story, including information about Chell's personal history.
Portal has won multiple awards for innovative design. Using a first person view and portals that allow one to traverse a room through one placed in one location to the other placed in another location to solve puzzles was and still is a very unique game design.