Portal 2 was challenging enough as space to worry about, but now we need to think about it time also?
Portal reloaded is a mod released on time too Portal 2’s 10th birthdayThis introduces a new set of test chambers and most importantly a new portal color. You will still be using the old blue and orange ones, but the green one that you get here too will let you step through time as you set up puzzles on a timeline and then move / solve them along two different eras, 20 years apart .
It even has a new voice acting and an original soundtrack. You can get it on Steam Here.