It has an expansion port, build-in OLED screen, Atmel MCU as screen driver/USB serial port converter and an SD card adapter for loading BIN, HEX and saving files or doing RAM dumps. The design is based on the classic Z80 (which they still manufacture believe it or not) and is quite small, only 3 x 3″. I’m doing a “build your own single board computer” workshop at the Midwest Gaming Classic 2020 in downtown Milwaukee this April.