I'm thinking on a sidescroller where you move a character with keys and you can draw some lines with the mouse. You can jump on those lines and they dissapear after a while, when you leave them or so. The goal of the game is to reach the exit gate in many small sceneries. The lines can be of different materials to change their behavior. Imagine an ice line witch you can draw as a slope down with a final slope up that makes you jump far after accelerating from the top. Or a rubber line that makes you bounce faster than the incoming speed. You can also use those lines for avoiding, trapping or killing the scenery enemies. The drawing ability is limited by length and you can increase it picking up items by the way. There might be a highscore table for each level based on the length of drawed lines.