One of the best ways to learn anything is to have fun while learning. Many moons ago Microsoft came out with a game called Terrarium. They used that to teach the world about .Net and C# programming. I remember building my scripts to control how your creatures interacted with the rest of the terrarium and all the other creatures in it.
Now, Screeps may seem new, but it is a recycling of the same concept. I’m not poo-pooing how cool it its. However they claim to be the world’s first MMO strategy open world game for programmers. Maybe they’ve taken a new concept from it but I have to say this has been done before.