Orbital Decay
Hundreds of moons in true n body orbits around a dying star. Click to throw in a rogue planet and watch the cascade.
A miniature solar system running real gravity. Hundreds of moons orbit a pulsing central star, and every body pulls on every other, so the disc is never quite stable. A gentle drag makes each orbit decay slowly inward, feeding the star one moon at a time and lighting it up in a flare with every meal. When two moons meet they shatter into glowing shards, and the shockwave nudges their neighbors onto crossing paths. Sometimes it ends there. Sometimes it becomes a cascade that tears a whole arc of the disc apart before the system slowly heals itself with new moons drifting in from the edge. Click anywhere to inject a rogue planet, a heavy white body that plows through the disc and drags whole orbits out of shape. Three rogues at a time is the limit. Throw in a fourth and the oldest one detonates.