--Totally Awesome OS -- Click green flag. The password is "Awesome" I just covered it up so no one can see your password. Press the ` key (the key just below esc) to close a window.
Btw, efficiency mode (In settings) basically disables all animations (Including the nyan cat video, but you still get sound), so you might not get as good of an experience. Although, if you have a slow computer, you might want to run it in efficiency mode.
