Portal 1 is quite fascinating for its mere 19 levels. The idea, the setting and the playstyle make it a good game, very good for the year it came out and still worth playing years later.
What I especially liked was how you could get used to the game mechanics throughout the first couple of levels, since it was the perfect pace. If you like puzzle games with a tiny bit of suspense then this is for you :)

This game is a lot of fun. The storyline is interesting, the characters too and the scenery is pretty cool as well, BUT I don't reccomend playing this game in multiplayer. The synchronisation with friends' games is not perfect and caused me to stop playing this game because we weren't able to continue the story all together and we did not know how and when it happened. Playing by yourself is safer for sure, though maybe less fun :')