Start with remainders less than 4 or 4 or greater. Other rules sort exact divisions from those with a remainder, or even from odd remainders. Zero is less than 4 and is even.
Choose a mode, rule and divisor. Settings offers dividend digits and card count. Press New Game to use your choices with a fresh set. Divisors 2–4 cannot produce remainders of 4 or greater, so those fixed choices are unavailable for that rule.
Clear answer removes the current unchecked answer and placement. Reset current replays the same cards. New Game clears answers and uses unseen calculations; if the available cards run out, change settings or reload to start a new session.
Use touch, mouse or keyboard: enter a remainder, then choose a group. Dragging is not required.