The guideline of physical computer proposed in the book Physical Computing by O’Sullivan and Igoe offers a basic idea of what function and compartments a physical computing device should have.Besides the detailed implementation of physical computing, such as the introduction of using circuit, microcontroller and chips, the core idea of it is still the same as the last reading about interactivity, that is, a device can receive an action, analyze is and give a reaction. Physical computing is much similar to a interactive device. Yet for physical computing, the action it receives and the reaction is gives might be best in reality. I mean not as data flows shown on screen, but real behaviors, like turn off the lights when heard a voice command of a human (a practical one) or play some music notes or draw a stroke on a wall (a more artistic one). In the other reading we can see lots of devices that are based on this idea, while using different hardware. Some of them are already widely applied designs that we might not think them as physical computing of interactive device, such as multitouch interface. Now even a mobile phone’s screen can accepts 10 fingers’ touch simultaneously. Other designs are also interesting, but are far away from us. The music devices are cool but not many people uses them, because their sounds are nevertheless less audible then real musical instruments, as they, after all, uses chip-generated notes. So an improvement of them might be combine the design with real musical instruments. Some of them are more artistic and beautiful such as the field of grass, therefore is a successful physical computing device as well. In general, physical computing can create unique art that cannot be imagined by the past people, different from drawings and music. On the other hand, physical computing can be practically used in daily life and have more down-to-the-earth usage. Both of them are good guidelines for designing our physical computing device.