According to Eq. 2, using an electronically excited state of a compound instead of its ground state makes ΔH 0 more nega ve. In the game, the player may access visible photons, 600 nm (199 kJ mol -1 ), UVA photons, 350 nm (341 kJ mol -1 ), and UVC photons, 180 nm (664 kJ mol -1 ). Overall, adding photons as reactants subtracts the corresponding energy from ΔH 0 and, as a result, from ΔG. In order not to make a LED as a "silver bullet" -a tool that can turn any endothermic/endergonic reac on into exothermic/exergonic, several rules and restric ons related to their use are introduced: