K-Sketch will allow ordinary computer users to create informal animations from sketches. Current tools for creating animation are extremely complex. This makes it difficult for designers to prototype animations and nearly impossible for novices to create them at all. Simple animation systems exist but severely restrict the types of motion that can be represented. To guide the design K-Sketch, we have conducted field studies into the needs of professional and novice animators. These studies showed the wide variety of motions that users desire in informal animations and indicate how to prioritize these types of motion. Our design allows the most important types of motion to be defined with pen gestures, and gives visual feedback for coordination of events.