My children are in primary school, and their hands-on ability is quite good. I want him to challenge in a more difficult way. I heard from my colleagues that the Baxter Robot Club in Yangzhou is quite good. Four and a half years old? Playing with robots? You are more cruel than the exam-oriented education in China! Ha ha, just kidding, it depends on how you define this "play". I hope your so-called robot course is not what I think. Robotics course belongs to the category of automation specialty, and the word "robot" has a wide range. You can try to let your baby play with generalized robots, such as smart cars and simple mechanical arms. If the baby is interested, he will get started slowly. If you want to learn, you have to start with the most basic single chip microcomputer, and you have to be able to write code. It is even difficult for non-professionals to guide you. And these things involve hardware and cost a lot of money. I suggest you know that the so-called robots that China college students play at school, such as "Challenge Cup" and "Freescale", are all aimed at college students, and many works are played. It is the result led by some experts and scholars. More professional: The best and earliest robot I know is Japan. They made great humanoid robots in the 1970s and 1980s. I don't think that industrial robots other than humanoid robots are strictly robots, but just some complicated manipulators. Among the books I know, Humanoid Robot (edited by Hideyoshi Ota, translated by Guan Yisheng) is enlightening in its kinematics analysis, which is theoretical and must be understood in theoretical research. In terms of practical application, the Department of Automation of the Chinese University of Science and Technology has a book about soccer robots and robot cars, named Design and Implementation of Robot Control System Based on 16/32-bit DSP (edited by Zhang Peiren et al.). If it is played by individuals, it can be used as a reference, because this kind of controller based on DSP is much easier to use than humanoid robots in big companies and big projects. I have limited knowledge and can only say so much. I hope I can help you.