The Demon Core

Simulation of a dangerous real-world experiment wherein you try to push a nuclear core as close to critical mass as possible by insulating its radiation.  Simply see how close you can get and survive.  

I may be pushing the game jam's theme of one-time use.  The wager for conducting the experiment is your life. The ultimate one-time use. As an added bonus for the theme, every play is a one time use as the application will quit if core hits critical mass.