Tip: refresh is safe—each game has a “New” button too.
Remaining stones: —
Allowed moves: 1, 3, 4
Math Insight (short)
Key idea: Classify each number of remaining stones as winning or losing (for the player to move).
Why it works: A position is winning if you can move to a losing position; it is losing if every move goes to a winning one.
What it teaches: Backward reasoning + state tables (a gateway to proof and discrete math).
Move history
Challenge: try several starting sizes. Can you predict which sizes are losing before playing?
Hint: build a small table from 0 upward and mark each state W/L.