probability - The frog problem with negative steps - Cross Validated
Triazzle® Puzzle - Frogs – Dan Gilbert Design
Amazon.com: Scramble Squares Frogs 9 Piece Challenging Puzzle - Ultimate Brain Teaser and Mind Game for Young and Senior Alike - Engaging and Creative with Beautiful Artwork - by B.Dazzle : Toys & Games
Six Jumping Frogs & the Aesthetics of Problem Solving