IoTtalk is a platform for IoT device interaction, which has been used to develop many IoT applications such as home automation. This paper uses Dandelion Mirror artwork as an example to show how interactive visual design can be conveniently implemented in IoTtalk. The Dandelion Mirror artwork conducts cyber physical interaction, which animates a dandelion in a mirror when a person smiles at that mirror. The dandelion grows larger as the person smiles bigger. The flower also vibrates following the heartbeat rate of the person. In our approach, the camera detecting the face expression and the heartbeat rate is considered as an input IoT device, and the mirror display for dandelion animation is considered as an output IoT device. In IoTtalk, the features of the dandelion animation are considered as the actuators that can be independently controlled. IoTtalk nicely connects these IoT devices, where various features can be created for interactive visual design with little or without any programming effort.