This paper presents a platform in which interaction designers can effectively and rapidly develop tangible interactive prototypes by sketching. The study aims to build a platform that plays the role of sketching in the hardware-software integrated interactive product design process. The platform consists of three components: a sketch based interactive concept exploration software application called STCtools, a set of physical user interface(PUI) widgets with a key converter and a video projection based Augmented Reality desk (ARdesk). For prototyping, a designer creates hardware and software sketches with pen based computers using STCtools. Sketches of hardware and software are drawn in a client device and composed in an electronic whiteboard, which is the server device. PUI widgets can be physically attached on a foam mockup or on a screen of the client device. The hardware-software integrated simulations are conducted on ARdesk. The sketch simulation is captured and projected onto a...