Correct answers are the only way to earn coins. Answers in a row climb the streak ladder: at 2, 3, 5, 10… in a row, every answer scores ×2, ×3, ×5, ×10… points (and a few more coins). A wrong answer resets it.

Pick a defender from the shop under the board, then click beside the path where its range circle turns green. Select a tower to upgrade it or change its target.

Each level needs a few correct answers before the next one opens. Enemies that reach the keep damage it.

Every level is harder, and level 13, The Unanswerable, cannot be beaten. Your score is your answer points plus points for every enemy your towers defeat.