Half Life 2 – The Stanley Parable v1.3

                    
The Stanley Parable is an experimental narrative-driven first person game. It is an exploration of choice, freedom, storytelling and reality, all examined through the lens of what it means to play a video game.

You will make a choice that does not matter

You will follow a story that has no end

You will play a game you cannot win

…it's actually best if you don't know anything about it before you play it 😀

TSP does not actually require Half Life 2 on PC, only the Source SDK which should download automatically when you start the game.