Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

🧩

Equivalence Classes & Fibonacci Sprint

Count a congruence-mod-n class's elements, or iterate F(n)=F(n-1)+F(n-2) from F0=0, F1=1 -- two chapters' own defined-structure counts.

⏱️ 75s

▶ Log in to play

← Back to the arcade