The website Who Am I is one that allows users to try to solve numerous mathematical puzzles. Upon entering the site you will see the image you see below where you will see multiple choices. The most commonly used button is the Play icon.
When students select the Play button they will see over 200 puzzles like you see below. The puzzles allow you to try multiple times until you get the puzzle correct.
As you can see above you also have the options to build your own puzzles as well as play bingo.
Embedded below is a 2 minute and 6 second YouTube tutorial.