2D Reaction Kinetics Gas Chamber

This 2D companion runs the same Arrhenius collision kinetics as the 3D original on a flat canvas: reactant molecules bounce inside a bordered box, and when two of them collide with enough combined energy to clear the activation-energy barrier Ea, they convert to product. Temperature sets how fast the molecules move and how often collisions clear that barrier, so raising it visibly speeds up the color change from blue (reactant) to orange (product) while the rate-constant and fraction-reacted readouts track the reaction live.