The mechanism for this game is the way that its shown with the camera view always remaining this way. Its constant through the game and its how it works and looks.
Another example to which Alan highly recommended I looked at was Fuzz Power.
This game was from way back in the 1990's and is a tale of a wild man's battle against a deranged cult of barbers. Again the mechanism is very much similar to Limbo.
Another example I've found of a simple mechanism in a game is in Candy Land which dates way back to the late 1940's.
The Mechanism here is that you draw a card, then move to the next space whose color matches that card.
So moving onto the idea for the mechanism in my game.
The idea I have been prodding at is about the view of the game. The idea is that its mainly a stuck camera view like Limbo or Fuzz Power but with a twist.
I should also mention here that even though its going to be a stuck camera the character is not stuck so the player could go all the way back into the depths of the game instead of being right at the screen.
The twist is that the player can move the camera by doing curtain things within the game and Ill give a few examples of what I have been picturing in my head.
Example 1 - Cut Scene - Mr Ninja & The Castle
So lets say Mr Ninja guy gets so far into the level an the next bit of the level is to climb up the side of the castle. There would be a quick cut scene to show the castle to which could show the kinds of routes you could take. This cut scene would not brake off from the game so the side view camera would zoom into and behind the head of Mr Ninja to show how he see it and then would move back. This would really only be used as the level end or starts.
Example 2 - General Play - Player Moves The Camera
So on general play a stuck side view would not fully allow me to fully utilise the game it self in regards to multiple choices on finding ways around people and places. So what I was thinking was to use/ place screens and watch towers (or other such items that relate to the culture) in the game so that the player could climb up in or hide behind them. But They wouldn't simply be used to hide in ow no, the player would then be aloud to see a 360 vision of the map around him to find the best routes it is at these point that the choices are made.
For example on the watch tower, you would climb up into it and have a look at the routes. The player would then choose options A, B or C to continue forward each having different out comes to the game.
An example for the screens would be that when you go to kill someone you can get behind the screen for cover so your not seen and also again look around the map so you can see everything that may make you want to kill the target, or spare them so some reason.
This game is all about choices, yes there will be a lot of killing and blood but whom you choose to kill and not will game the game.
An example of this is this:
Someone asks you to remove a guard as they have annoyed him. So you can simply kill the guard to which removes him from the game or drug him so it looks like he was drunk so he is fired. Thus keeping him in game. The choice is not always obvious as in this case he would at some point find you and try to kill you for making him lose his job. So maybe killing him was the better choice there?
But then again the player may not have known that there was a 3rd option here. You could have killed the guy asking you to remove him thus again keeping the guard in the game but this time he would later appear and help you get through a tuff place to get past in a later level.
But on saving him fully and his job by killing the guy asking you to remove him you get others trying to kill you.
So each choice you make in whom you kill and how and whom you do not will change events. Same goes for the route you take as you may pick the one that looks the easiest but induing so may end up on the hardest and miss out on another event that happens on another route.