UPDATE 27/07/2016 2.43am: Edmund Mcmillen has confirmed to Eurogamer that this untitled game will be on PC and Mac for sure. Consoles are "a big possibility", but it's too early to confirm anything at this stage.
McMillen also noted that this game is not Isaac related and that it uses the same character from his early browser-based platformer Time Fcuk, though it isn't a sequel.
"No name yet so we are just leaking out early teases for now, all I can say is I think most would describe it as a Mega Man / Isaac-like, but a platformer with really tight controls," McMillen told us.
When asked how this would affect development on The Legend of Bum-bo, McMillen said "Deving both at once not sure what one will be out first, but I'm quite happy with the pace of both currently they seem neck and neck but we will most likely push one back a month or two from the other when the time comes."
ORIGINAL STORY 26/07/2016 11.39pm: The Binding of Isaac creative lead Edmund McMillen has teased a new project that he's working on with Closure programmer Tyler Glaiel.
Revealed on the Binding of Isaac blog, this upcoming project looks like a platforming shooter set inside a giant rotating cylinder. It's also got pretty cool music and this video snippet teases what appears to be a boss fight.
Bear in mind that whatever this game is, it looks different than the "turn based puzzle RPG type thingy" The Legend of Bum-bo, which was announced earlier this year.
It's unclear what platforms this new game is coming to, when it will be released, or if it's set in the Binding of Isaac universe. We've asked McMillen and Glaiel about this and will update should we find out more.
McMillen also teased a bit of new content for The Binding of Isaac's upcoming DLC Afterbirth+.
Afterbirth+'s new character Apollyon's starting item is the Void, an item that destroys all items in the room, but gains the power of each destroyed item. So if you vanquish a useable item, each time you cast Void you'll also perform the effect of the item you previously obliterated. This will stack too, so by the end of the game casting Void could be very powerful and have any variety of effects.
If the item is not usable, however, destroying it with Void will offer a random stat bonus. One side-effect of Void is that it turns all pickups into swarms of blue flies.
Another usable item Afterbirth+ will bring is Smelter, which destroys all trinkets you are currently carrying and offers their effects to your character permanently. This will be an item found in stores (as opposed to Void, which is the starter perk for Apollyon).