Pentagon 15
Cool math story this week about the discovery of a 15th tiling of the plane by a convex pentagon. For more, see the Reddit story (https://www.reddit.com/r/math/comments/3fe347/15th_pentagon/) or Wikipedia page (https://en.wikipedia.org/wiki/Pentagon_tiling). There is no wiggle room - this is the pentagon up to similarity. Fun angle chasing problem to use the tiling to see how the angles are determined. I’m not sure of the wallpaper group, can you tell?