Sue Ausman found mathigon--textbook-of-the-future:

• Significantly builds student knowledge“My gifted students love the interactivity of several links and the puzzles which are very open ended.”
• Significantly improves teaching efficiency and productivity“It is easier for me to use the website to demonstrate math concepts than to try and show students. The website is laid out very efficiently.”
• Does not significantly save school money
• Does not provide school data
• Significantly teach-problem-solvings
• Significantly improves creativity and critical thinking“Puzzles develop critical thinking in interesting manner.”
• Moderately improves creativity and critical thinking“Puzzles develop critical thinking in interesting manner.”
• Slightly improves parent engagement“Students are very interested in the puzzles, but some may not be task committed enough to follow through. That’s typical of gifted students.”