Move the slider to change the number of sides and build a regular polygon, then try naming different polygons and telling convex from concave in the quiz below.
A polygon's name is really decided by one very simple rule: counting how many sides it has. 3 sides means a triangle, 5 sides a pentagon, 8 sides an octagon, and so on. As long as a shape is surrounded only by straight line segments, the number of sides and the number of corners are always exactly the same.
A polygon where every side is the same length and every angle is the same size gets its own name: a regular polygon. Polygons are also split into convex and concave โ if there's no spot that caves inward in any direction, it's convex; if even one spot caves inward like an arrow, it's concave. Every regular polygon is convex, but a concave polygon can never be regular. Move the slider to change the number of sides and see the shape's name and whether it's convex or concave for yourself.