Well I had that period In my electronics life :D when I wanted to build something with the simplest digital components possible... I played around a lot with 74 stuff, build some 7-segment displays counters. My biggest project was a digital function generator with 1Khz-20Khz output. It was based on a 3-NAND gate generator controlled by potentiometer, binary counter EEPROM memory with sine wave samples and D/A converter. So as basic as It can get ????.
Unfortunately I have never build a physical version, It was only a design project, but I have some photos of me building and measuring the 3-NAND generator. Also my PCB design skills were mediocre so the layout and routing of this board is not the best.