1A2B — Bulls & Cows

Remember playing this with a pencil in the back of class? Each of you hides a secret number, trading guesses turn by turn — first to crack the other's code wins. That game now lives in your pocket.

The rules take 30 seconds: A = right digit, right spot; B = right digit, wrong spot. Use those two clues to crack the secret number in as few guesses as you can. Simple rules, pure deduction, minutes a round.

— DAILY CHALLENGE
One puzzle a day, the same for everyone worldwide. Build your streak and share your result with friends.

— PLAY THE SAME PUZZLE TOGETHER
Share a game code or QR with friends and everyone gets the same secret number. Deduce on your own, then compare who cracked it in fewer guesses. Great for parties, classrooms and group chats.

— 3 TO 10 DIGITS
Start easy with 3 digits or push your limits at 10. From casual to hardcore.

— PENCIL & PAPER TOOLS, BUILT IN
The best part of 1A2B has always been scribbling notes while you deduce — so we built it in:
• Digit marks: one tap crosses out digits you've ruled out, or circles the ones you know are in
• Position notes: jot candidate digits for every slot and narrow the answer down step by step
• Notes save automatically with each game — leave and pick up your deduction right where you were

— AND MORE
• Full guess history — see every step of your deduction
• Stats and win rate to track your progress
• Hand-drawn notebook feel, like deducing on real paper
• Fully playable offline — commutes, queues, bedtime

Ready? Today's number is waiting.