Here's my draft (always) design doc for my personal project Desk Marble.
The Player moves objects usually found inside an old desk drawer around to slow a marble dropped down through the inkwell. 3D game where the (camera follows the marble down the hole into the drawer), and as seen by someone looking into the drawer.
Select, move and place objects with mouse, rotate with keys. On screen button to drop the marble and pause game.
During the game, a marble travels through the maze created by the placed objects. Marble is dropped into inkwell and must reach a target (A hole in bottom of desk drawer).
And the goal of the game is for the marble to take the longest time through the maze without stopping. A stopped marble resets the level, after a pause and a button click.
Sound of marble dropping, rolling, hitting objects, reaching target. Particle effects and animation when object is placed.
A special sound for when the marble slows to a stop. Feature Creep: Close up follow marble and lighting for a closed drawer.
Levels start with just three or four objects (a book, ruler, pencil and eraser). Each level adds more items making the maze more complex.
Feature Creep: Random initial object placement.
Feature Creep: Multiple marbles. Smaller target.
Feature Creep: Larger drawer with more objects!
Feature Creep: Multiplayer and/or Networked version. Slow races where the winner is the last one to finish.
The timer will increase until the marble reaches the target.