Love the concept as an incomplete Chemistry student.  I haven't verified your reactions (I have always been more into organic), but the inspiration with collision theory and thermodynamics is very vivid. I admit I couldn't reach Supernova. At times I was't sure if it's better to spam click, or click on select atoms to transform them into reactive ones. At every stage I would end up with more and more inert particles making it more difficult to push it through the next threshold. By the time of last stage the Supernova threshold seemed virtually impossible to reach. I wonder if it's by design or is it for potential rebalancing.