**The Challenge: **Build yourself a wobbler. Wobblers are 2 circle (or 2 ellipse!) constructions that have a constant center of mass. Or rather, a center of mass that doesn’t move up and down as the wobbler rolls. Thus, resulting in a satisfyingly continuous “wobble”.

*Materials Needed:* cardboard, ruler, boxcutter or scissors*Math concepts* *you could explore with this challenge: *algebra, angles, circles, geometry, proportions/ratios, symmetry, vertices/intersections