I made a pop-up card that spins as you open it!

It uses a geometric mechanism invented by an unknown student at Musashino Art University in 1988! Instructions here: http://www1.ttcn.ne.jp/a-nishi/popup_spinner/z_popup_spinner.html

Home > Geometric toy > Popup Spinner

Another surprising result from computational origami: If you fold a piece of paper correctly, you can cut out arbitrary shapes with a single, straight cut! Even multiple ones! This is possible for all shapes!! :O
@blinry WHAT
@uberardy @blinry My thought exactly
The Fold-and-Cut Problem (Erik Demaine)