Created by Daryll Strauss of Los Angeles hackerspace Crash Space, these open source boards come four to a pack and are the perfect large-group build for people just learning to solder. They’re easy to assemble, and a hundred people building them can collaborate to create gigantic, blinking trails of light. Best of all, to see the dominoes fall another time, you don’t have to stack them all back up. Just press the first domino’s button again.