Pop-Up Mechanism
A mobile paper-engineering puzzle where you place and size real pop-up mechanisms (v-fold, parallel fold, box, pull-tab, rotating disc) on a page and drag the hinge open and closed. Badly proportioned folds jam or lie flat, and mechanisms that foul each other when closed light up red. Twelve levels ramp to a three-mechanism capstone, ending in a shareable opening animation.
Created by haojie.huang
