Portal 2

A very cool first person puzzle game, probably one of the best ones out there. If you like puzzle games, you're absolutely going to LOVE this masterpiece!

The game was created by valve in 2011, 4 years after the release of the first game.

Story introduction: 
After killing GLaDOS in the first Portal game, Chell is put in suspension for 50 days, then she's awakened for a mandatory physical and mental wellness excercise. After the player learnt the basic controls, Chell needs to return to her bed.
After an unknown amount of time (presumably after more than 100 years) she's awakened once again. For her surprise, someone's knocking on the door. After opening the door, a core comes in on the management rail. This core called "Wheatley" wants to escape, so he helps Chell get to the testing track in hopes she would find the Portalgun, and they could leave the facility using this gun. The whole place is overgrown and messy, because there was nobody to maintain the place after the death of GLaDOS.
After some warm-up tests, you and Wheatley find yourselves right next to GLaDOS' room. Wheatley isn't aware of the fact that GLaDOS is shut down, he only heard rumours of it which he didn't think were true. After crossing HER chamber, you two get to a room with tons of switches. Searching for the switch "Escape Pod", Wheatley accidentally turns on all the switches and the powerup of GLaDOS begins.
Chell and Wheatley can't stop this process, and GLaDOS wakes up.
She is really salty about the fact that you killed her in the first game (which is understandable), so she's very cynical towards you and mocks you throughout the whole game with sassy and mean comments.
After her short dialogue, she throws you in the incinerator room to find the Dual-Portal Device, and the tests begin!

Characters:
Chell - the mute protagonist. Her personality is not really well known.
Wheatley - the blue core. He was made to be dumb but his ego is too big to accept it.
GLaDOS - a maniacal robot who wants to test at any cost. Very cynical and funny, passively agressive. Later in the game her personality starts changing, and it's the biggest character developement in the entire game. She starts thinking like a human in the end.
Cave Johnson - a genius scientists who does everything to reach his goals. He started his career with shower curtains, and later founded "Aperture Science Innovators". He was making human experiments, and he knew what he wanted. He's already dead during the story of the game, you can only hear his recordings.
Caroline - the assistant of Cave Johnson, and has some other important roles that I don't want to spoil in this review.

Content: 
The goal of the game is solving puzzles using your 2 portals. The orange one, and the blue one. You can shoot them on certain surface, and the way they work: you go into the orange one, you come out of the blue one. If you go into the blue portal, you come out of the orange one. Momentum is preserved between portals.
The game has an amazing, 7-8 hour long single player campaign and a very fun cooperative campaign that you can play with your friends. And one of the best parts about the game: infinite content, you can create your own testchambers and publish them, you can play chambers made by other people, and the Portal 2 community is still very active since 2011, so you'll never run out of maps!

Overall:
I can only recommend this game, this is my favourite game of all time, and it's just brilliant. Never had more fun with any other games. It contains everything I want from a game: thinking, a deeper story beneath, fun gameplay, various elements, "create your own map" function, infinite content, multiplayer, and one of the best voice lines I've ever heard in games.
My ratings:
Gameplay: 10/10 (there isn't anything about the gameplay I wouldn't like, it's just perfect)
Graphics: 8/10 (still pretty good compared to being a game made in 2011)
Sound: 10/10 (I can't emphasize how good the voicelines were, it was a masterpiece)
Content: 9/10 (infinite content, replaying the game to find easter eggs and find achievements, but the puzzles are way easier when you already know the solution)

Steam page of the game: http://store.steampowered.com/app/620/Portal_2/

Thank you for reading my review!