This 2D simulator recreates a cloud-to-ground lightning strike from first principles: an electric field builds between the negatively charged cloud base and the induced-positive ground below until it approaches air's breakdown threshold, at which point a fractal stepped leader — generated by recursive midpoint displacement, exactly like a real channel's random jumps and branches — gropes downward step by step. The moment it reaches the ground, a return stroke rockets back up the ionized channel at roughly a third of light speed, delivering the blinding flash, the current spike and the 30,000 K heating that make the crack of thunder. Adjust the charge rate to make storms build faster or slower, dial the branch density to see sparser or busier fractal channels, and force a discharge on demand to watch the whole leader-to-return-stroke sequence play out immediately.