For the theme of "Deeper and Deeper", I went with The Core - The Game. The objective is to get to the center of the Earth, drop some nukes to restart the core spin, and detonate them. Don't worry about getting back out, that was not part of the plan.

Controls:

Mouse: Control direction

W/S: Increase/decrease speed

Spacebar: Action key (drop/detonate nukes)

Escape: shows mouse which is hidden since your mouse moves the cam Clicking in the game window will hide the mouse