Catelite, I believe this would be neat but a pain in the arse to code. Also, have you noticed on the "WHAT NOT TO SUGGEST" topics that Periodic table elements can be easily covered by just a few elements we have.
H2 should fuse when the temp is over 7000 Degrees, and the pressure is about 100 atm. It should stay on the screen as a invisible particle (just for about 5 sec) that generates pressure and heat, and have the pressure and temp be the games max.