I've noticed that my son spends way too much time on YouTube or playing Minecraft and one of the few offline activities he enjoys doing on his own is coloring. And since he comes to me every time he wants a new coloring book and we spend about 10 minutes together searching for each picture, I made a website with a collection of coloring books for him. The site is very simple, but to be honest, I haven't had so much fun with the process of creation for a long time.
https://colorango.com/