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.
I only give it that few points because it's mainly about jumping!
You have to jump here an hour and there! You have to think for half a minute to get the solution but half an hour to xecute it, because its only about difficult jumping that has to do with a big load of luck! not more. Many ideas are awesome but that jumping sucks and ruins everything