Excellent game.

Kill your enemies, and your computer.

It's easy to say that this game is very difficult. But, if you are one of the people who can fight through the enemies, this is recommended.

No Steam library is complete without this game.

It's quite short, but if you were smart enough to get to the end you would most likely understand the fun level editor.

Good game, you can destroy buildings and your FPS.

If you thought the first Portal was good, this is much better. It has fun physics-based puzzles throughout the game, along with a very good story.