A difficult shot--possible but unlikely

How does one handle difficulty of an action in DW?

In one scene, the charcters were rushing to stop an ogre from cranking up a drawbridge. The theif declared that he threw a rock aimed at jamming the gears of the crank. I allowed this and he got a clear success.

I didn't think much about it until after he succeeded. If I had been playing any other game, I would have put major minuses on this action. He had no special moves applicable and it seemed possible but unlikely.

What would be the best way to handle this in DW? I wonder if there's a general rule of thumb. I can think of other examples -- like jumping a chasm that is just wide enough to challenge a long jumper.

 

First, the narration.  How wide was the distance described?  How small was the target?  Is the character a halfling (known for their throwing skill?) or has that character established some particular skill at chucking stuff?  Are there circumstances that would indicate success at this straight-up?

No? Oh, okay.  Well, check out the tags, first.  Do you think the action fits the tag?  That's good - I mean, if it were a long throw you probably just fail.  Shame, that.  If that's fine though, maybe it's time to go to the dice.

Is there a specific move to be made?  Did the GM prepare a when you hurl a rock into the gears move?  Does she want to make one up right now? 

No?  Is there danger here?  Sounds like there might be.  What is it?  If it's, say, "the ogre closes the drawbridge, meaning we're delayed and the prince inside the castle might get turned into ogre food" well, that sounds like a thing worth Defying, to me.  With DEX.  Via the rock, if it makes sense.  There needs to be a clear thing that happens if you fail and maybe the GM has an idea of a 7-9.  Maybe you slow the gears but don't stop the bridge entirely, or maybe the ogre has friends on the parapets who'll chuck stuff down at you as you run across.  Etc etc.

Yeah, all that makes sense. Like, the Ranger's Called Shot ability is perfect. If there's no particular Move for it, then remember that Dungeon World isn't a game about simulation or skill granularity. It's a game about epic adventure, so define the risk and the reward and don't worry too much about the exact difficulty of each and every action.

Usually, like in combat, it's the fictional details that make something more difficult. For a straight hail Mary pass, it's probably enough to say something like "Well, you're gonna have to stop and aim so carefully to pull this off. If you miss this, that ogre will be on top of you." Otherwise I think it's legit to just be like "no way can you pull that off" if you have to. DW doesn't really do the whole "you need a natural 20 for this" thing.

Don't worry about modeling difficulty or applying minuses. Just be a fan of the character and make their lives interesting. They're risking enough when they take action; there's no need to penalize their cool shit.

Yeah, recently the thief in my game decided to clamber across a thin goblin rope, 30 or 40 metres up, spanning the width of the large cavern; then he swung on to the Bloodstone Idol's crusty clay shoulders, looped a long length of rope around it's 8 metre clay neck and used his own body weight and pendulum force to slice the Bloodstone Idol's gigantic head clean off its shoulders.

I was a little incredulous at first but kept reminding myself how cool it would be if he pulled it off. So I didn't set a difficulty level or anything, I just asked lots of questions about how he was doing it and asked for few rolls, which in the end was more than enough. The last roll was a 7-9, and I offered the ugly choice of something in his pack shattering (and o man did he have some choice loot) or d6 damage from the fall. I knew he had 5 HP so I thought he might take the damage, and he did and rolled a 6.

He didn't go through the black gates but did come back a changed man. I thought it was pretty epic result in the end. A crazy idea, worked and paid for in full.

The constant risk in DW is that no matter what action you take, things could go very badly, very quickly. The difficulty is baked into the fiction, into the consequences of PC actions, both expected and unexpected. It's less a question of "Can I do this?" and more "What's it going to cost me to do this?".  

Asking questions helps set character precedent.  Making little notes like "is proud of his skill at archery" or "is known as a philanderer" can definitely help you gauge difficulty and plausibility later, when those actions come up again.

It's less a question of "Can I do this?" and more "What's it going to cost me to do this?". 

This summarizes it nicely, I think. Skinnyghost brings up a good point, too. You can totally make some assumptions based on the character's description and style, even class. Can the cleric make that shot? Maybe not. The halfling thief on the other hand...

Maybe I'll sound harsh and bad GM, but what I think is very important to understand in *World games is that there's much more "yes, you do that, you don't need to roll", "yes, you have to do this, and then you have it, with no roll" and "No, you can't do that, it's not possible for you now" then in your average rpg. That's OK.
Rolls do not have to be made as often as D&D. Even half as often. And so you should not be ashamed of saying "no, you can't do that." Because it's what makes it realistic sometimes - inability to "just throw dice at it".
Now it should not be you halting the adventure to full stop, like "you left your bow at home, so you can't stop him, so you suck". On the other hand, you should provide them with different solutions if you have so much as shadow of idea that they don't see a way through. Maybe "No, you can't stop this gate from closing with this rock. But there's got to be another way in. Like sewer exit."

Because sometimes you need to make them think, and too often throwing dice is the opposite of thinking

I like that post, Guns-n-Droids. I hate saying no to a player and I try to never do that, but you know what I hate more? When a player says "Well, I'm gonna try to use Diplomacy to make the King give us his army. I could always roll a natural 20!" It pulls you straight out of the fiction in a sleazy way.

If something is flat-out impossible, it's totally legit to say no. In the OP's example, I think using +Dex was the right way to go. But sometimes you totally gott call bullshit on someone, it just happens.