Raspberry Pi, the most popular single board computer for hobbyists and students, is very affordable platform and it is a popular solution for retrogaming. Nowadays modern free and open source tools allows us to develop Raspberry Pi add-on boards to improve the gaming experience. Over the years the community has already created numerous awesome hardware projects for cases, add-on bards and peripheral optimized for retrogaming. The focus will be on providing guidelines and recommendations how to use the open source EDA software KiCAD to design open source hardware gamepad as a HAT (Hardware Attached-on Top) according to requirements of the Raspberry Pi foundation as well as a simple cases for laser cutting or 3D printing with another popular open source software tool OpenSCAD. Using practical examples related to retrogaming you will understand how to create device tree binary overlay for mapping keys and how to flash it in EEPROM attached to pin 27 of 28 of the Raspberry Pi header. Exact steps for setting up and using our do-it-yourself gamepad with popular GNU/Linux distributions RetroPie and Raspbian will be provided. Last but not least we will discuss the benefits of using open source hardware and the certification of the Open Source Hardware Association (OSHWA). The presentation is appropriate for anyone interested in low-cost retrogaming and modern free and open source software technologies. No previous experience or hardware knowledge is required. Apart from retrogaming enthusiasts, the talk is appropriate for wide range fo developers, makers, and students.