Cloned Cube is a Portal mod. It takes place after GLaDOS' fall in Portal. You assume the role of Chell's secret clone. You have to escape or else you may just be tested to death. There is one obstacle. CUBiS is trying to kill you.
The second update to Cloned Cube, download with 7-zip to your sourcemods directory.
More info on this update here.
Requires Portal and only works on Windows.