"The cake is a lie!"
It is, but Portal does not lie as it truly is a good game! While short, its puzzles make it an interesting game so much so that you'd immediately want to do a 2nd walkthrough. Also, there is a way to replay several of the so-called "chambers" but in a more difficult version.
I'm not sure if this has mods like its sequel - nevertheless, it's worth completing this one before moving on to the next as the puzzles are even more difficult and diverse in Portal 2.
I like how the game has a background story while it would not be necessary, at all. It has an excellent antagonist in the form of an A.I. called GLaDOS.
Portal is a memorable experience and if you liked Half-Life you should pick up this Valve product, as well.
Oh, you didn't like Half-Life? Then, please go and have a cake. :)
PS: I'm not sure why I have zero hours logged for this game. Probably because the logging system was introduced after I completed Portal. In any case, my review is based on a gameplay time of roughly 15-20 hours.