Do-it-yourself solar system

If you’ve always wanted to build your own solar system, roll up your sleeves — it’s time to see what you’ve got. SuperPlanetCrash is an online solar system simulator, set up as a game. The goal is to plop planets around a star and keep them orbiting for 500 years. Seems simple enough, but gravity is a formidable opponent. Each planet or star adds to the gravitational tug-of-war with every other body. Get the balance wrong, and planets crash together or are flung into interstellar space.