Blue Portals is a unique Portal mod that has players traverse through new test chambers using only the single portal device and many new test elements.
What made Portal so much fun was that you had to carefully think about where to put your portals. Once you had that, it was trivial. This mod is well made, but it isn't very much fun. It's all about the precision execution of portal jumps. It's got some cool ideas and neat mechanics, but it loses the cleverness that made Portal great. You don't have to think very hard to solve the puzzles, but they are difficult to execute properly. I was pretty dissapointed by this mod. If I wanted to try a manuever over and over again until I got it right, I'd load up Quake Live to practice strafejumping. On the bright side, I found no bugs, and the test chambers looked nice.