I'm Ethan from Design Squad, and that's Kieran.

We're making a Rube Bl... (laughing) We are making a Rube Goldberg machine.

Rube Goldberg was a cartoonist... ETHAN: ...who made cartoons with complicated machines in them.

KIERAN: It's a chain reaction.

ETHAN: One thing leads to another thing and it leads to another thing... ...to make a simple task really complicated.

So ours is going to just turn on a fan.

It starts with a guy sitting in a chair, and he pulls a string... KIERAN: ...which pulls this train that goes down a ramp.

ETHAN: The spoon will knock over these VHS tape dominoes.

We were going to use little dominoes, but we needed bigger dominoes for a bigger force.

ETHAN: And then this heavy PVC pipe falls and hits this pad.

It will compress air and launch this foam rocket off.

KIERAN: It pulls this plastic tube up.

ETHAN: The golf ball will go down this... KIERAN: ...and into this cup that pulls a string, which pushes this ball onto that ramp... ETHAN: ...which will knock over more VHS tape dominoes, which will knock over another pool ball attached to a string, and that string will pull a lever... KIERAN: ...and turns the switch to turn the fan on.

There are quite a few simple machines in our chain reaction.

A lever, a pulley, a ramp... We're using gravity a lot.

I'm going to pull this string.

We don't want failure, but it sometimes happens.

Failure.

No!

It didn't work.

Oh!

Fail number five.

We learned from the failures and we just have to fix things.

So what happened is it got caught on the pillow and didn't fall all the way to the ground, so what I'm going to do is I'm going to move everything a little bit.

I'm so hot, but I can't reach the back of the fan!

I know how: I'll pull this string!

(fan whirring) Fan works.

Instructions to make your own chain reaction are not going to be on the Design Squad website.

Make it yourself!

(sighs happily)