"No eyes, always watches!"
As you are told when you start, your only goal in this game is to wander around this dark, fenced in woods and find the 8 pages scattered throughout the forest. That's really it, there's no weapons, no jumping on platforms, no goal to reach; just simply walking around in the dark looking for notes such as "leave me alone" or "don't look or it takes you." In fact, there's no way to win either; even after collecting all 8 pages, Slender Man still gets you anyway. No reward other than the satisfaction of finding them all.
So yeah, the gameplay sounds pretty simple and shallow, but that's not the draw of this game. The game focusses more on the atmosphere around you. When you start, it's awfully quiet; you hear crickets chirping in the distance, and the night sky is dark and almost clear. It seems like a nice and calm game, right? You will wander for a bit and notice a note on a tree, car, oil tank, etc.
Upon picking up the mysterious note, you will start to hear an eerie drum beat. Your adrenaline hits the roof as you start to wonder if you are truly alone in this forest. Eventually, as you keep wandering and pick up more notes, you will notice the drum beat becomes more intense and terrifying. In between all this you will notice your view getting fuzzier every now and again but you can't ever look behind you because HE could be right there, ready to take you.
Given that this is such a simple game and all, it does succeed at what it tries to do most; the game is actually scarey. This is done well thanks to the creepy and quiet woods around you. The atmosphere pulls you in, and finding your first note really helps get your adrenaline going as you try to avoid getting caught. In the end, you will jump almost every time Slender Man comes across your view, and it's scarier that you are completely defenseless and your only option is running away as fast as you can. I don't even feel it is right to describe Slender Man himself to you, for doing so would spoil the surprise.
However, it could have been just a little bit scarier if the model for Slender Man were just a bit better. He looks ok, but compared to the scenery around you, he looks a little clunky. Improving his model could have made this game more effective than it already is.
As a game, there really isn't much gameplay available here as the objective and controls are simple. As a paranoia horror game, Slender hits just about every nail on the head; from its intense audio and visuals to its creepy atmosphere. For a free game, this is worthy of your time; whether you are familiar with the Slender Man myth or not. It's especially a great game to show your friends and family when they're over.