So what happens if someone cant do something?

For example how would you deal with someone kicking down a door , or trying to steal something ? In a d20 game you would roll a skill check to see if something occurred but in this game there are no such things. I have read the beginners guide, and that actually provoked this line of thought. In that guide there is a part where the thief wants to get a jewel from a statue, the author says he can, but what if he can't? What do you do ? Just say no you can't or what?

There has to be a good reason that the character can't, but remember that even in D20 if a player says "I turn myself inside out and hide inside of my own internal lining!" or some such thing, you should just tell them that they can't, so this isn't a unique thing to Dungeon World. What is unique to Dungeon World is that, when a player wants to do something that doesn't make sense or shouldn't be possible, you should usually use the "Tell them the requirements or consequences and then ask" move.

"You want to kick down that door? You probably could, but it would make a loud noise, and it will be too damaged to lock again . . ." The Fighter has a move that lets them control the circumstances of breaking down doors and such, so that they can avoid unfortunate outcomes like that.

For stealing something, if nobody is watching and the object is something the character can carry, of course they can steal it! If they need to take it without being noticed, they're actually triggering the Defy Danger move, where the danger is being noticed.

If you can't do something, then the GM should tell you that.

An important way to look at things: you're rolling if there's a consequence of failure, so if the character's attempting something with no consequence, just make a judgment call. Like the Fighter's Bend Bars/Lift Gates move, the consequence can be as little as destroying something or making some noise. No roll should end in a roadblock; failure means something bad happens. It's an important distinction.

Sometimes it's just "No, but if you could change X, Y or Z then maybe?"

My initial thought was why is the GM putting a door in front of the fighter that he can't kick down. Maybe there's a fantastic reason, but usually a door that he can kick down is much more interesting. I'm a fan of the fighter and his door-kicking self.

What I'm really wondering is does the game cater to the little extra things. For instance the jewel in the eye socket example. In a normal d20 game the person would roll a str check , if they didnt meet the strength check then they didnt get the jewel, if they DID then they got a little extra treasure. How does Dungeon world handle these things ? These optional things that are there kind of as a bonus . Do you just always give them the jewel? I understand that a 6- is failure , a 7-9 is "yes, but..." , and a 10+ is success. But there seems to be no check for this. How do I know if they can take the jewel without consequences , take it but have to pay a price, or not be able to take it at all?

Should I just make up a move for it, assuming my party likes these kind of little extras?

If there's a possibility of negative consequences when they decide to take the gem, they're defying danger. If there's no possibility of negative consequences, you should just let them have it. But why put a huge gem that might be a pain to steal in a room unless you want to lure your players into doing something dangerous?

"Why put a gem in a room if it's not dangerous?"
I like to build my worlds with a lot of extra things, I dont thing -everything- needs to lead to danger. Somethings should just be there to make the world feel a bit more real. Sort of sandbox..y.

"Why put a gem in a room if it's not dangerous?"
I like to build my worlds with a lot of extra things, I dont thing -everything- needs to lead to danger. Somethings should just be there to make the world feel a bit more real. Sort of sandbox..y.

Putting a big gem in a statue, with no risk, is like doing this to them.  Which is awesome.
http://oglaf.com/trapmaster/


(Note: this particular page is SFW. Rest of that site: NSFW.)

LMFAO. That's amazing!

Look, they say "I'm going to get. That gem!" You, the GM, have decided there's no trap, there's no guard, there's no risk of falling, getting attacked, breaking something, angering the gods. So, no danger. No danger, no Defying Danger. No move.

There's no move there.

If they aren't triggering a move, then you just ask them to describe getting the gem out and you describe how the gem comes out. Or, if you've decided that they can't possibly get the gem out, you narrate them not getting it.

Moves aren't about "can you do it?" They're about what happens when you try.

(@Jeremy, that's hilarious!)

Right, so basically it has nothing to do with how strong the character is numerically. If there's no trap the GM gets to decide, and the decision is irrelevant to the mechanics?  Is this correct?

Sure, but if he lacks strength, then it's a good opportunity for the GM to ask the obvious "how do you get it out, little man?" In fact it might be a good time to show them the downside of their class (like if its a wizard, how does he climb up to the eye socket? How does he pry out the gem without tools? Etc.)

I think its simply a case of let them get the gem... Then ask questions, of the characters and your own prep (stakes).
So, [paladin] you saw the thief pry the gem from the socket of that idol, right? What do you think about that?
So you have the gem, what do you want to do with it?
So that gem the thief garnered, it feels magical... you know something about its history yeah [wizard]? Wanna Spout Lore about it?

So you missed your [roll sometime later in the dungeon]? That gem you recovered from the idol? It seems to have literally burned a hole in your pocket and disappeared... [Hmmmm, who else wants that gem and why?]

Its never just a little extra on the side. If it's narrated into the story, make it stick, re-incorporate, ask questions.