Recs.
Updated
Portal 2 is a first person puzzle game with a humorous story and endearing characters. The gameplay focuses on solving fun and well designed puzzles, by placing adjoined portals with your portal gun.
SpecsUpdate
Pros
Pro So large in scope that it takes multiple playthroughs to see everything
Portal 2 is larger in every way when compared to the first title, from the longer and more detailed story to the larger levels and new game mechanics. This makes for a title that will last 8-9 hours minimum, with many elements that are worth revisiting, not to mention the co-op section of the game, which is separate from the single player story.
Pro Huge selection of user-generated content that should appeal to any use-case
The game has more than 60,000 co-op puzzles created by users through the Steam Workshop and through mods. Because it is user-generated content, the quality and size of these puzzles vary widely, including everything from simple, one-off chambers to full-fledged expansions with high-quality stories, voice-overs, and new gameplay elements (for example, Mel). By having such a selection of content, there should be something that appeals to just about anything someone is looking for.
Cons
Con Late game single player can be quite difficult
While the single player learning curve is quite gradual, late game the puzzles can become quite difficult, sometimes leading to the player being stuck for long stretches of time. While not impossible to solve, some creative thinking will need to be done in order to finish.