I have been experimenting with Arduino's for a long time but I never managed to finish a stand-alone project. I chose to make a hex game as I really liked the concept and would like to be able to convert between number systems quickly in my head. I wanted it to be compact and battery powered. I also wanted to convert between hex, decimal and binary in all directions.
I started with an Arduino nano and a smaller 128x32 OLED. The binary input was made with 8 tactile switches. I tried using a pot to do the hex input, it worked but I was never really happy with it. I had a simple piezo speaker that beeped when you got the correct answer.
I had been wanting to try using an ESP32 and found a feather clone with built in battery charging, I thought this would be a good fit for this project.