make a phffff nuclear planet only made from plut isoz deut etv.
BluBubblz: I'm making this
eh both are too difficult, maybe something more weapon-related?
Or make a sort of radio broadcaster that uses photons, with the ctype being the "message." Maybe build a small town with a broadcasting station and houses with receivers.
Make a thing that turns water into electricity. Sparking water with iron makes hydrogen and oxygen. Gold prevents corrosion of iron. Platinum produces electricity from the gaseous mix. You'll be left over with only hydrogen, which can be burnt and then plant turns the smoke back into oxygen. Good luck!