Mostek MK3850 Single Board Computer with tiny BASIC.
Based on Tetsuya Suzuki's F8SBC.
Assemble the firmware with the Macro Assembler AS.
Here's another F8 based single board computer. that's even simpler to build.
tiny BASIC
Monitor
MK3850 SBC CPU
MK3850 SBC Memory
MK3850 SBC GAL16V8
MK3850 SBC LEDs