Since everyone, their mother, dog and evil clone has already made one. Here is yet another Slenderman clone, featuring Derpy!
Derpy vector by http://nebulonb100.deviantart.com/
Music and sound effects are from Newgrounds and freesound. Full credits are in the game.
The space panorama in the end is from the European Southern Observatory. Credit: ESO/S. Brunier
The image of planet Earth is from http://en.wikipedia.org/wiki/File:The_Earth_seen_from_Apollo_17.jpg