Welcome to the Gigatron!
The Gigatron TTL microcomputer is a minimalistic retro computer. It is special in its own oddball way, because it has absolutely no complex logic chips in it, not even a microprocessor! Instead, its CPU is built out of a handful of classic 7400-series ICs, colloquially known as the TTL logic series. In the Gigatron these simple chips not only form a CPU, but this CPU in turn performs all tasks that normally require dedicated peripheral chips. Despite its simple and small design, the Gigatron works as an 8-bit single-board microcomputer that you can play video games with.
Now you can build one yourself. Learn what happens inside a CPU and enjoy playing the built-in retro video games or write little programs in BASIC. You can also hack it in any way you like if you have a taste for that.