Julian found mathigon--textbook-of-the-future:

• Significantly builds student knowledge“Taught me fundamental ideas behind parts of calculus”
• Significantly improves teaching efficiency and productivity“Very well put together textbook style learning, interactivity greatly enhances knowledge retention”
• Significantly teach-problem-solvings
• Significantly improves creativity and critical thinking“Interactivity”
• Moderately improves creativity and critical thinking“Interactivity”
• Significantly improves parent engagement“makes math more fun”