Who needs Mario Maker? The BBC just released a tool that makes it easy to make Doctor Who themed games, and had the limitless gall to name it Doctor Who Game Maker. It's intended to get younger folks into coding and making games, but anyone can start using it now.
The whole thing works in the browser, and you're initially confronted with a choice between an arcade mode to play through other peoples' creations, or making and sharing your own content.
There are a whole bunch of tutorials, starting with basic stuff like building small levels and getting steadily further into win/lose conditions, logic, and physics. Some of them are basic text pop-ups, and some of them are videos.
You can even start doing the tutorials without signing in, though you'll need to do that if you want to save or share your creations.
All the assets available are Doctor Who themed, but there's nothing saying the mechanics have to be. It can pretty much be whatever you want, and more importantly it gets kids thinking the right way -- a great primer for something more complicated like Game Maker.
You can check out the tool here.