I just today managed to find all of the secrets in Ed McMillan’s bizarre action-roguelike, The Binding Of Isaac, and so I thought it would be just and right for me to pass on the wisdom I’ve assembled during my numerous attempts to kill Isaac’s Mom. Due to the random nature of the game, this isn’t going to be like a traditional walkthrough: No two playthroughs of The Binding Of Isaac are alike, and so strategies that might work on some occasions won’t apply to others. Think of this more as a series of (light on spoilers) top tips and tactics that you might not have considered, or just tricks you might not have discovered yet. If you’re just looking the basics, Ed’s got you covered on his blog here, and this wiki is a useful encyclopaedia of everything in the game (although obviously it’s filled with spoilers).
Isaac and all the other characters are fairly weak to begin with, but as you gradually kit yourself out with more and more powerups as you progress through a playthrough, if you play your cards right, you can become hugely powerful. Remember: Since the which items you are able to get in any given playthrough is randomised, you can’t expect to get everything you’d ideally want each time, it’s all about making the most of what you’ve got.
Shoot the shit
The, uh, piles of poo that are scattered around the levels always have a (slim) chance of containing items, same goes for any fires. Sometimes they drop coins, bombs, hearts or keys, and if you intend to have best chance to buy cool items, blast through obstacles to get more pickups, survive and open locked doors/chests, you’ll want as many of these as possible.
Find the secret rooms
Every floor has a secret room, which are more often than not filled with money, or an item. They will usually (possibly always: I can’t remember one ever not being) be in a square on the map that is bordered by three other rooms, and you’ll need to use a bomb on the section of wall you think that hides the entrance to them. If you’ve got more than enough bombs, and you don’t mind using up a few of them to get a reward, it’s worth trying every place on the map that could hide a secret room. There are a few enemies that leave bombs behind when they die, and if you are quick you can push them towards the wall, to test for a secret room without using up your supply. There are also enemies that explode upon death, and these can be used in the same way (just make sure that they are in the right position when you kill them).
Getting across gaps
Often there are gaps in the ground between you and an item you want, there are a few ways you can get at these. If you get one of the items/powerups that allow you to fly (either permanently, or temporarily) you can fly right over them. If you get the ladder powerup, you can use to to get over any one square gap. Failing either of those, if there is a rock next to a gap, putting a bomb on the opposite site of the rock to the gap will knock it into the hole, letting you get across.
You might want to get straight to the boss fight as soon as you see the entrance to it’s lair, but often it’s better to explore the floor fully before going to battle with the boss. You definitely want to try and find the treasure room before tackling the boss, and there’s often nice rewards for exploring fully. I’d only say that on the latter floors, were any given room could have multiple bosses hiding in it, is it really worth heading straight to the boss room, but it’s up to you whether you think it’s worth it.
Save your pennies
It can be tempting to spend your coins as soon as have them, but at the very least I would suggest that (unless you’re in desperate need of a particular item there and then) it’s best to save your coins until at least you have cleared out every room. Perhaps there is some really expensive item that you might be able to afford if you don’t buy cheaper items early on. If you’re really low on health, and you find a slot machine or arcade room, a big stockpile of coins could sort you out (they will probably pump out some health if you keep pumping coins into them for long enough).
Same goes for keys and bombs. The first treasure room won’t be locked, but later on the will sometimes be locked, so I’d suggest trying to keep at least one key on you at all times (instead of using them to open chests) otherwise you might have to miss out on an upgrade. Obviously it’s a gamble, and it’s possible that a chest might actually contain a key (or several), so it’s your call. Bombs can be useful in combat, especially for some particularly enemies, but unless you’ve managed to collect loads of bombs, it’s a good idea to be sparing with them. A lot of this is down to personal preference and playstyle, but it’s worth trying to be at least a little conservative.
On unlocking the extra characters
I wouldn’t bother too hard in going out of your way to unlock the other playable characters, for the most part they will unlock through natural play. One of them unlocks when you collect 55 pennies, which you will do instantly eventually when you get the (very rare) dollar item (worth 99c).
Blow things up
If you’ve got no use for the slot machines, blood donation machine, beggars or the guessing game in the arcade can all be blown up to drop items. Obviously you can’t use them once you’ve blown them up, but it’s worth doing if you are done with them anyway. It’s worth saving blowing them up until after clearing a floor, because even if you think you have no more use for them, they might be useful later.
Very occasionally it’s possible to get into a glitch room: A room filled with loads and loads of items. I’ve only ever managed to have it happen once in all my playthrough, and it happens totally randomly when you use a teleportation card like hermit or the moon.
Carefull dealing with the devil
After defeating a boss, sometimes a room opens where you can sell a bit of your soul in exchange for a powerful item. It’s often worth considering (and even just going to take a look, and shooting the fires out whilst you are there), but because you are paying with some of your health bar, unless you’ve upgraded your health plenty, you’re taking a big risk. It’s worth experimenting, but on the whole I’d say more often than not, you’re better off walking away, however tempting it may be.
Leave soul hearts til last
Unless you’re terribly low on health, the blue temporary hearts you can pick up are best left ignored until you’re ready to face the boss. They’ll still be waiting for you whenever you’re ready for them, but if you pick them up immediately, and then get hit, there is no way of recovering them, whereas if you leave them, get hit and lose some of your regular health, you will likely be able to find a recovery heart at some point, then go back and get the soul heart at your leisure.
That’s your lot, hopefully if you’ve been struggling there is something here that might help you on your quest. No doubt you’ve got some useful strategies to share too: I’d love to hear any more tips in comments. There’s a content update due out tomorrow, so there’ll be even more secrets to discover.