It sounds like something manufactured by Nintendo, but SuperPlanetCrash is the brainchild of Stefano Meschiari, an astronomer at the University of Texas at Austin. The online game offers a novel challenge: Design your own solar system and make it last for 500 years. You might think it’s easy to plop a few Super-Earths and giant planets around a single star. But think again. Each planet you place in your solar system exerts a gravitational tug on the others. It doesn’t take that much for one of your dwarf stars to collide with an ice giant.

More than 2 million systems have been created since the game made its debut in April. You start with an Earth-mass planet and begin creating your own solar system. The larger the planet and the more you’re able to plop into your construct, the higher your score. If you prefer, a drop-down menu of actual planetary systems offers a template with which you can tinker.