A logic puzzle with a twist. Every board can either be covered with dominoes or be proven impossible, never both. Find out which, and prove it in as few squares as you can.
cover it
…or prove itTwo ways to win
You never know in advance which kind of board you're looking at. Start laying dominoes, and the board tells you, if you listen.
Drag across two neighbouring squares to place a domino. Cover the whole board and you win. A square with only one free neighbour decides its own domino, so the forced moves are where to start.
Mark a squeeze: a few squares that together have fewer neighbours than there are of them. They can't all get a partner, so no covering exists. Tip the balance scale and the board is stamped NO WAY.
Every board is fair. A mathematical guarantee (Hall’s marriage theorem) says exactly one of the two always exists, and a solver checks every board before it ships. The fewer squares your proof needs, the more stars you earn.
Features
The same daily board for everyone, fresh at 05:00 UTC. It gets harder through the week, from a Novice board on Monday to an Advanced boss on Sunday.
Solve the daily on its own day to grow your streak and fill this week's coins.
Three stars go to the shortest proof the board allows. The result screen can show you the sharpest proof once you've won.
Stuck? The owl's three-step hints nudge you without giving the board away. Hints never cost money; they only cap the stars on that board.
Novice 30, Medium 60, Hard 60 and Advanced 50, each tier introducing new ideas: forced chains, pockets, counting proofs and more.
Daily, streak and total-star leaderboards, plus achievements for your first proof, ten sharpest proofs and finished tiers.
Screens
Premium
The daily board, Novice and Medium are open to everyone. Premium adds depth, never an advantage: hints and leaderboards work the same for everyone.
$0
A complete game, with light ads between boards.
$9.99 / year
Starts with a 3-day free trial.
$9.99 a year is the US price; the App Store shows the price in your own currency. Premium renews automatically unless you cancel at least 24 hours before the end of the current period, and can be managed or cancelled any time in your Apple Account settings.