Local co-op coming in The Binding of Isaac's remake may sound jolly exciting but are you concerned that having help might turn the roguelike-like into a game for, not just about, babies? Relax! Take a chill pill, pal. Designer Edmund McMillen has explained how it'll all work and, from the sound of things, Rebirth's co-op will bring the joys of friendship without necessarily losing the thrills of trying not to die. See, calling in a baby friend (no, co-op players actually are babies) will cost a slice of your life, and they may come with a terrible curse.
Co-op players steal a heart away from player one when they join, and while the baby gets the same abilities as Isaac currently has (or whoever you're playing as), both deal reduced damage. Babies are drawn from a sizeable pool, which mostly look different but may be "special" or "cursed," he explained in yesterday's blog post. "So there is just as much of a chance in spawning a baby that will randomly spawn a troll bomb every 1-2 min. as getting a baby that heals p1 when it dies."
Player one is also in charge of items, activating them for both at the same time, so there's a risk of bombing each other and whatnot too. Should you bomb your baby or they otherwise die horribly, they'll respawn as a new, different baby.
It does sound like co-op will still be a bit easier overall, mind. But that's fine, possibly even great. McMillen calls it "an awesome way to get new players into the game." Here, have an animated gif: