First, I watched Ben Eater's fantastic YouTube series.

Then, I made my own and improved it, incorporating some of James Bates' improvements and some of my own, including an esp8266 (Wi-Fi) program loader.

I added a web-based assembler, based on customasm. 

Then, I wrote an emulator for it in C.

Then, I wrote a web front-end for it.

This is the result.

A breadboard computer that you can program, in your browser!