It's been over a month since Nintendo released Super Mario Maker, a game that lets you build your own Mario levels. In that time, I've been trying to find time to write a review of it, but it's taken me this long because I can't stop playing this game. It's captured my imagination in a way that probably no other game has before, and it's finally Wii U's "killer app" to show why its tablet-meets-gamepad controller lets players do things no other console can offer.