Control 4x4 LED matrix. I built this to teach simple coding skills. Kids can easily edit the array and see the lights they want. I build this for an ESP8266 D1 Mini. Code can easily be modified for other boards. I wrote another version of the code that allowd user to upload changes via wifi. I found this to be more trouble because I was often showing the board in different locations and would have to connect to the wifi on my phone to get it to work. This version is simple and straight forward.
Instructions: Upload the Matrix_4x4_No_Wifi.ino file to your board using Arduino.ide.
I have shared the circuit I built for the D1 Mini. This board uses 3.3v. I used 5.5 ohm resistors on my first design and the LEDs were too bright to see the paturns. Later I used 500 ohm and it was much better.