The board
A grid — usually 9×9 — with three kinds of occupants:
- Noughts (○) — your targets. Clear all of them to win.
- Numbers (1, 2, 3, 4) — your pieces. Each number is its move distance.
- Blocks — unmovable walls, until you mine them.
Movement
Drag a number in any cardinal direction — up, down, left, or right. A 1 moves one square; a 2 moves two; a 3 moves three; a 4 moves four. You can’t stop short, and you can’t slide diagonally.
The four rules
1. Number → Space = Number + 1
Landing on an empty cell upgrades the piece. A 1 becomes a 2, a 2 becomes a 3, a 3 becomes a 4. A 4 stays a 4 — you can’t go higher.
2. Number → Nought = Number
Destroys the nought. The piece lands there with its value unchanged. This is your primary offensive move.
3. Number → Same Number = Number − 1
Both pieces merge, and the destination becomes one rank lower. Two 3s collapse into a 2. Two 2s collapse into a 1. And — critically — two 1s collapse into a fresh nought.
4. Number → Block = Nought
The piece is consumed, and the block becomes a nought. Why would you want to do that? Because sometimes the only way to clear a corner is to create a nought in a useful spot.
Goal
Clear every nought on the board — including any you create along the way via rules 3 and 4.
Pass-plus (the hidden depth)
Rules 3 and 4 can both produce new noughts. Solving a puzzle often means creating extra noughts and then clearing those too. A good solution doesn’t just mop up what’s there — it reshapes the board on the way through.
Tips
- Work backwards from the trickiest nought, not the easiest.
- Save your 1s. One careless upgrade and you’ve lost granularity.
- Merges are escape hatches: two stuck 3s become a more mobile 2.
- If a nought is unreachable, the fix is often to mine a nearby block.
Two modes
Daily Challenge — a curated puzzle, designed with a known solution. Same puzzle for everyone, every day.
Enigma — randomly generated from a seed. No guaranteed solution. For when you want a real fight.