this is heavily based on slock and, just like it, locks your X11 session until the user is typed. the only difference from the original is that it doesn’t require you to press once the password is typed. you just type it and wait (waking the screen sometimes takes a bit).
this difference between both programs is actually quite handy: we all want the screen to go off, not only black, being this the only way to truly save the life on those pixels. the problem is that returning from this state sometimes takes time, at least for me, having to wait as much as ten seconds for the screen to show color. impatient people tend to believe, during this time, that the screen is still locked, so they type the password again, and again hit enter. now imagine you blocked the screen while on a irc chatroom! yeah!
in the future i should replace this with a patch to slock, as it makes no sense to fork the program just for this added characteristic.