So we have the player character, one object, and a 2D environment. This looks like the setup for a puzzle game. The room will be constructed as a single-room platformer, but with a focus on the object-based puzzles rather than jumping puzzles.
The shape and size of the object needs careful consideration, because it will change the nature of the puzzles significantly. A well-known but unconventional shape, such as the L-shaped Tetris piece, would lend itself to more creative puzzle generation.
> Is It… Alive?
The player’s first encounter with the object will be when they walk by it and it is enclosed in a cage. The player’s second encounter with the object will be when they walk past the cage again, and it is broken. The object sits beside the cage. The player will then encounter a puzzle that requires the object to solve in a simple and obvious manner – such as a hole in a wall with the same shape as the object.
As said before, the nature of the object will be a mystery. As well as moving on its own offscreen, I would like the player to encounter a puzzle with the object already at the end and an indication that it had solved the puzzle for you before you got there. The motivations of the object are left ambiguous.
The end of the game would involve leaving the object behind.
> Depth and Complexity
It is important to keep the ideas of depth and complexity in mind when constructing a puzzle game. A game has depth when there are a small amount of mechanics that work together in increasingly complex ways without introducing more to the player, and complexity refers to the sheer amount of mechanics used.
Complexity isn’t bad, but it can be hard to handle – especially in a short game like the one I’m pitching. I will focus on its depth; on the range of things that can be done with a small group of rules.
Thomas Was Alone; Portal; Journey; Limbo; Undertale; Super Meat Boy.