On the Subject of Kyudoku
"Ichi, Ni, San, Yon, Go, Roku, Nana, Hachi, Kyu"
This module shows a 6x6 grid with digits in each cell.
Whenever a digit is pressed, the digit toggles in this order: digit, crossed-out, circled.
Circle every digit from 1 to 9 exactly once in such a way that the sum of the circled digits in each row and column is equal to or less than 9.
After every correct digit has been circled, the module will solve.