Baka_Ouji's Portal Review
Everything to say about this game has already been said. It's a fun and unique puzzle game even to this day, over a decade after its release, and will leave you feeling fulfilled despite its short run time.
Give it a go, Valve basically gives this game away on Steam and it can be run on basically any modern computer, I remember the first time I played this was on an awful dingy little laptop and I got by just fine at 30FPS.
Only complaint is that replayability isn't really high for me with this one. Once I've beaten a puzzle, that's kind of it for me, and anytime I go back it's just too simple and I get bored. But, for the current price it normally goes for, that's not really an issue.