Braid, which came out years ago was a quite brilliant platformer and the designer Jonathon Blow has used the money from that to spend the last half decade to work on this project: The Witness. It's a first person puzzle game which has you taking on a number of logic and environmental puzzles in a small island map, with some sort of sinister back story.
The graphics are beautiful and the puzzles are clever and tough. I've not played a game in ages where I've needed a notebook to scribble on as I worked on the puzzle solutions (it's a nice way to kill the commute).
I'd completed it in 2 weeks but that's not a reflection of how short it is, more how much I was playing it. I did have some marathon weekend sessions on it, it was that addictive. Reading forums there are rumours and conspiracy theories that there is a lot more that has been missed, such is the interest in the world that Jonathon has created.