In a recent blogpost on the Binding of Isaac: Rebirth website, creator (and co-creator of Super Meat Boy) Edmund McMillen teased a new project. It's a collaboration with Closure programmer Tyler Glaiel, and while McMillen didn't really say much about it, it's likely to be the cylindrical platformer he teased last year.
"...not many of you know this but Tyler and i have been in crunch mode for the past 3 months trying to finish this secret project," McMillen wrote at the weekend. "We are coming close to announcing it and its release date, so keep an eye out for it, i don't want to spoil the fun yet but i can say this."
"It's hard, it's weird, it's personal, it has amazing controls, it's a totally new unannounced IP and it's easily one of the largest games i've ever made level wise."
Of course, there's every possibility that this new project is something we've never seen before, but here's the brief footage of the McMillen / Glaiel project that was teased last year: