This website was created by two teachers in Massachusetts, who take problems that they love, and adapt them so that they are accessible to everyone. They design posters and handouts that hook you visually and explain the problem in just enough words. The problems that they pick require trying, struggling, failing, adjusting, and trying again until, finally, a discovery is made. Here are just a few examples of what you'll find:
Sankaku puzzles are geometric based logic puzzles that focus on finding the area of a triangle. The goal of each puzzle is to connect three dots to form a triangle with the specified area.
(See the list above for a virtual version of Sankaku puzzles using DESMOS)