gamemaster tips

Don't out-step your character's scope of knowledge, especially not for the sake of tutorial.
They should only say what would make sense for them to say. At least try to give them the illusion of freedom, hide the answer(s) among equally interesting options, give them a reason to want to do the thing, interchangeable  flavortext story doesn't count, unless it directly impacts processions , don't hand-feed the answers to them, waiting for vulnerability is not a very interesting main tactic, don't tell them what to do, give them options and let them get lost exploring until they find their way, let the environment invite possibilities, have backup plans and contingency plans for "important" things.
Start with a goal, whip up a layout, add properties to the objects, keep track of them when they are in range of effecting things. Invincible walls are a poor protection. instead of simply disallowing wall breaking, try to instead make it disadvantageous to break walls.
Filling the walls with furbies, electrically charging the walls, put lava on the other side of the wall.... there's all sorts of things you can do to prevent stuff while preventing ooc frustration. Give the players the tools and stage props to lead the action. Give them options!
Even the most mundane items can bring joy if they can do at least one thing. it doesn't even have to be an immediately important thing, but it can still be useful much later. As a sidenote, old items should be able to shine even after their initial debut, preferably used in new interesting ways. It should be more than just a key, it should be a variable possibility.
Reward them for their inventive solutions, but don't make the reward the whole point of the thing.  Balancing between balls hard and easy to follow is difficult, but worth striving for.