Alice already delivered information about how co-op will work in Binding of Isaac: Rebirth, but if you weren't paying attention at the back of the class, perhaps you'd like to see the mode in action. Designer Edmund McMillen has played the game for seconds shy of eight minutes, showing off some of the new co-op challenges, items and abilities that extend the Nicalis'-developed game beyond "remake" territory into the well-established "remake-sorta-sequel-sorta-standalone-expansion-sorta" territory.
Anyway. Watch the video below. It's got about a million tears in it.
Because tears are bullets in Binding of Isaac.
The way co-op works is that the additional player steals a single heart from player one upon entering the game. That means that player one has two instead of three hitpoints and their co-op partner - who in this instance is a floating troll-baby who uncontrollably poops occasional bombs - has just one. Should your baby die, they'll respawn as a different kind of baby, but only if player one has a heart to spare for them. As you'll see in the video above.
The original Binding of Isaac was built in Flash as a quick project by Edmund McMillen and Florian Himsl, after the release of McMillen's Super Meat Boy (which was made with Tommy Refenes as part of Team Meat). Rebirth is a full re-code of that original game, to solve a bunch of problems native to Flash and, while at it, add a bunch of new stuff. It's due out later this year.
McMillen continues to work as part of Team Meat of course, on the on-hold Mew-Genics and on the just-announced A Voyeur for September, which is maybe a game and maybe an anagram of Super Meat Boy Forever and therefore a viral marketing campaign. Who knows, videogames? Who knows.