Investigating the Puzzle of Portal

In portal, you play as a character called Chell. You wake up in a test chamber, with a slightly creepy robot named GLaDOS. She explains your situation and you are released into the first puzzle. The game starts off easy, with you having to place a "Weighted Companion Cube" on a button. In the next level you are introduced to portals, and just a few levels later you get your first portal gun. This allows you to shoot a portal and run through it to go to the other. There are 19 test chambers where you solve increasingly more complex puzzles. It's a shockingly challenging game on your first play-through, and it will definitely take you a few hours. However, replaying the game proves to be incredibly fun, and attempting to beat a time proves really challenging. However, this game does hold some slight issues when it comes to age ratings. Primarily, that the game can, (And almost certainly will on your first play through) contain blood. This happens in a few chambers that contain turrets, who will shoot at you and blood will spatter across the screen and walls. As always, judge for yourself how much this will affect you. A second issue is the slight creepiness of the story. GLaDOS is an unsettling character, often saying threatening and creepy things to Chell. The 3rd issue is the difficulty of the levels. Some can get confusing or irritating, but most won't really cause a challenge. 

Now to answer the question very very few people were asking. What age rating should portal be? Currently, it is at a rating of 11. Personally, apart from the blood, the game really won't be anything the average gamer hasn't seen before. Because of that, we think that portal will be ok for 9 years and up, as long as they do not struggle with blood.