Parity

Parity is a 3×3 numbers puzzle built in plain jQuery. Every number on the board is a power of two. You select a cell and push it up or down one step — halving it or doubling it.

Your goal is to make every row, every column and the four corners add up to the same total. Because doubling and halving are inverses, the whole board carries a conserved quantity — and finding that invariant is the game.

Parity ships with a long campaign of hand-designed puzzles in its level data.

How to Play

1. Click a cell to select it.
2. Use the up and down controls (or the arrow keys) to shift the number one power of two up or down.
3. Watch the row and column totals update as you go.
4. When every row, column and the corners match, the level clears.
5. Press Next level to continue, or Reset to start the current puzzle over.

Controls

• Click a cell — select it
• ↑ / ↓ or the on-screen arrows — double or halve the selected number
• R or the reset icon — restart the level
• N — next level, once solved
• Swipe support is included for touch devices

Tips

• Start at the corners. They are in two lines at once, so a change there fixes two constraints for the cost of one.
• The sum of all nine cells never changes under doubling/halving (a halved cell hands its excess to nothing — the total drifts, but the product of the cells is invariant). If you are stuck, that invariant will tell you which moves are even possible.
• Work backwards from the goal. If the target totals require a 16 somewhere, that 16 has to survive every move you make.
• Halving a 1 is not allowed — 1 is the floor, not a step.

Save Data

The current level and your progress are stored in your browser's localStorage. Clearing site data will reset it.

Open Source & License

Parity was created by Abe Fehr and is licensed under the MIT License.

• Original game source: https://github.com/abejfehr/parity
• Original live build: http://abefehr.com/parity/

This integration self-hosts the MIT build so it runs entirely in your browser. The game bundle is byte-for-byte unmodified. Only the surrounding page was edited, to remove the original page's Clay analytics, Facebook SDK, Like button and AdSense unit, and to fix a root-absolute favicon path.