Look through the plastic sheet. Everything looks magnified! It's fun to have your friend look at your face through it, it makes your face look weird.

The sheet is called a Fresnel lens. See the circular ridges on the sheet? That's the secret of the design of the lens, which makes it possible to create a lens that is very flat. Usually lenses are made using a thick, solid, curved piece of glass or clear plastic. That type of lens is not flexible, and requires a lot of material to make. A Fresnal lens is made using a lot of thin circular pieces, all angled the way they would be in a thick lens. Imagine taking the surface of a regular lens, slicing it in circles, and pushing it in towards the center, removing material from the bottom of each column until all that's left of each circular ring is a little angled wedge.

Fresnel lenses were originally created to make huge lenses for lighthouses that would be thinner and use less material, so they would be less expensive to make. Even today, it's very expensive to make large glass lenses. These days, Fresnel lenses are commonly available as "full page magnifiers" to help people read text. Fresnel lenses are also used in VR headsets!

• Fresnel lenses are available cheaply as "full page magnifiers".

You might want to duct tape the edges to help prevent breakage.