Score
0
Time
90s
Best
—
Two-colour connection puzzle. Fill every cell with a dark or light stone so each colour forms one connected group and no 2×2 block is a single colour. Solve as many as you can in 90 seconds.
Tap an empty cell to place a dark stone, tap again for a light stone, and once more to clear it. Locked stones are given and cannot change.
Two rules define a solved board. Every dark stone must connect to every other dark stone through edges — up, down, left or right — and the same for light: two single groups, no islands. And no 2×2 square may be entirely one colour.
A cell glows red when it breaks a rule: a 2×2 block of one colour, or a pinwheel (a 2×2 checkerboard) that would trap a colour and make connection impossible. When the grid is full, any stones cut off from their group light up too.
Fill the board correctly to score, and a fresh puzzle appears at once. Solve as many as you can before time runs out.
The 2×2 rule is your fastest source of certain moves. Whenever three cells of a 2×2 already share a colour, the fourth must be the opposite — otherwise you complete a forbidden block. Scan the board for these near-complete squares first; each one hands you a free stone with no guesswork.
The pinwheel trap is subtler but just as strict. If two diagonally touching cells hold one colour and one of the other diagonal is the opposite colour, the last corner cannot complete the checkerboard, because that little windmill seals a colour into a pocket it can never escape. Learning to spot pinwheels early stops you from painting yourself into a dead end.
Think of each colour as water that has to stay in one puddle. Before you drop a stone that would wall off a corner or a narrow neck, ask whether the trapped side still has a route back to the main group. A single stone in the wrong place can strand three or four others, and on a full board those orphans are exactly what the red highlight reveals.
In the timed mode, speed comes from chaining forced moves rather than solving the whole grid at once. Fill in every certain 2×2 conclusion, watch how each new stone creates the next forced square, and let the answer cascade. Save the harder connection reasoning for the few cells that the local rules leave genuinely open.