This seems like it should be doable. Essentially, a flat, top-down view of a character, his/her point of view shown from a flash-light, with everything else blacked out that isn't within the direction of the camera. The map would be randomly generated, and the Slenderman would be set as a randomly-teleporting entity that would appear anywhere, with a more focused attack/appearance when the character is nearing an exit/finding most of the notes.
Obviously this is the same as the 3-D version of the game in thought, but would be playable on newgrounds or on a tablet/smart phone in concept.
I don't have any java/programming experience, but the idea is free for the taking. I'd only like credit for the thought, though I'd not be surprised if someone is already preparing this very program right now. If not...heck, it should have been already!