What the Marshmallow Challenge is
It's a design exercise used in classrooms, workshops and corporate away-days. Teams get 18 minutes and a small kit, and have to build the tallest freestanding structure that holds a marshmallow at the top. When time is called, the tower has to stand on its own — no hands, no leaning on anything.
- 20 sticks of uncooked spaghetti
- One yard of tape
- One yard of string
- One marshmallow — it must end up on top, whole
The exercise was developed by designer Peter Skillman and popularised by Tom Wujec in a widely-watched TED talk. Stanford's d.school publishes it as a free teaching tool.
Why kindergarteners beat business school graduates
This is the finding the exercise is famous for, and it's the whole point of the debrief.
Young children build and test constantly. They put the marshmallow on early, see it sag, and fix it. Adults — especially ones trained to plan — often spend most of the 18 minutes agreeing on a single ambitious design, then place the marshmallow in the last thirty seconds and discover it is far heavier than the structure assumed. There is no time left to recover.
The lesson isn't that planning is bad. It's that when you're working with an untested assumption, prototyping beats planning, because the assumption is what kills you.
The engineering underneath it
Underneath the team-building, the challenge is a genuine structural problem, and three real principles decide who wins:
Triangles hold, squares don't
A four-cornered square can lean over into a parallelogram without any of its sides changing length — nothing resists it. Add one diagonal and it can't deform without stretching that brace. This single idea separates towers that stand from towers that fold.
Weight has to reach the ground
Every joint's load needs a continuous path of struts down to something solid. A beautiful top section with nothing carrying it is just a heavy hat.
Cantilevers fail at the root
Anything sticking out sideways concentrates its bending force where it attaches, not at the far end. That joint is where it breaks — which is why marshmallows perched out on an arm bring the whole thing down.
Playing it as a game
Spaghetti Marshmallow takes those mechanics and makes them playable. Drag to draw a spaghetti strut, tap to drop a marshmallow joint, and build up to the goal rings — then hold every ring for three continuous seconds while the wind blows.
It runs on a real physics engine, so nothing about the collapse is scripted. A bare square really does rack and fold; add one diagonal and it really does hold. Spaghetti bends and snaps under load. Marshmallows never snap — they squash and re-grip, like the real thing.
To be clear about what it is and isn't: this is not the literal 18-minute exercise with a timer and a tape budget. It's a puzzle game built on the same structural ideas, with 80 levels that get progressively meaner about them.
For teachers and facilitators
A few ways people use the game alongside the real activity:
- Before — a few minutes of play makes bracing intuitive, so teams arrive with an instinct rather than a blank page.
- After — during the debrief, it's a fast way to show why the towers that failed did. You can rebuild the failure and watch it go again.
- Instead — when there's no budget, no spaghetti, or the session is remote.
It's free, needs no accounts, and runs in a browser on school hardware. There's nothing to install and nothing to buy to play it.
Common questions
What is the Marshmallow Challenge?
A team-building and design exercise. Groups get 18 minutes and a small kit — typically 20 sticks of uncooked spaghetti, a yard of tape, a yard of string and one marshmallow — and must build the tallest freestanding structure that supports the marshmallow on top. The structure has to stand on its own when time is called.
How long is the Marshmallow Challenge?
Eighteen minutes is the standard time limit. Most facilitators add a few minutes either side for setup and for the debrief, which is where the actual learning happens.
Why do kindergarteners often beat business school graduates?
Young children tend to build and test repeatedly, putting the marshmallow on early and adjusting when it sags. Adults more often spend the time planning a single tall design and place the marshmallow last, discovering only at the end that it is heavier than they assumed. The exercise rewards prototyping over planning.
Does the marshmallow have to be on top?
Yes — a whole marshmallow, at the highest point. Cutting or eating it is the classic rules-lawyer move and it doesn't count.
What's a good height?
Around 20 inches is a solid result for a first attempt. Practised teams go considerably higher, mostly by bracing the base properly instead of building taller.
Can you play the Marshmallow Challenge online?
Yes. Spaghetti Marshmallow is a free browser game built on a real physics engine, where spaghetti are the struts and marshmallows are the joints. It is not the literal 18-minute exercise, but it tests the same structural thinking: brace your build or watch it fold. Play it here.