Hey, thanks for the question. Designed for 2+ players, but playable with just one, as long as you don't might playing against yourself (much like in a tabletop wargame where you might play both sides).
Given that the Kids dictate what happens to the Witches when they overstep their boundaries; and the Witches know what the Big Bad is, it works best if there are two of you. But playtesting I played both sides. It works. It's just less fun.