A back-of-the-napkin sketch is one of the most popular ways to explore and share a rough idea. But if the idea is about something dynamic, like a clock or a dance, static sketches can only get you so far. In this video we introduce Inkling, a tablet-based “programmable napkin” that enables users to sketch and play with dynamic systems. The magic of Inkling comes from constraints you can draw and manipulate so quickly and fluidly that you could do it over a beer, in support of a conversation.