One rule, understood in a single tap
com.kulor.flod
Your territory starts in a corner. Each turn you choose a colour, and every matching tile touching your area joins it — the colour spreads outward in a wave. Keep choosing well and the patch grows until, in as few moves as possible, the whole grid is one colour.
There is real logic underneath. The board floods deterministically from your region, a move counter runs against the target par, and every level is solvable inside its budget, so beating your best is planning rather than luck. Dozens of boards climb from small and gentle to large and knotty across easy, medium and hard, with a daily board, an undo for rethinking a turn and a fresh shuffle always one tap away. English and Danish.
Flod on Google PlayBuilt with nothing behind it
Everything the game needs to remember — which boards you have finished, your best move counts, the board you are part way through, your settings — goes into the app's own private folder on the handset, which Android keeps sealed off from every other app installed. No account is created, no identifier is issued, no event is counted anywhere, and no advertising library is compiled into the build.
The app declares no internet permission at all, which Android enforces at the level of the operating system: it cannot open a connection, whatever its code might intend. The trade is that progress lives on the phone and nowhere else — worth knowing before a handset is replaced rather than after.
Flod is published by a Danish company. The privacy policy names it in full, along with
the address to write to.
A game made entirely of colour, which is worth thinking about
Around one man in twelve and one woman in two hundred sees colour differently, most often at the red and green end — and a puzzle where colour is the whole of the information is exactly where that matters.
Flod ships colourblind-friendly palettes for that reason. They are in the settings rather than buried, and switching to one changes nothing about the logic of a board: the same moves solve it.
Why a board has a par at all
The moves a shuffled board forces on you before you have played badly
Take the shortest route from your corner to the far one and read the colours along it. Wherever two neighbouring tiles differ there is a boundary, and here is the useful part: a single move can carry your region past at most one boundary on that route. So the number of boundaries along it is a floor on the number of moves — not an estimate, a floor, true for every player and every strategy. On a shuffled board those boundaries are easy to count exactly, because along a path the "differs from the next one" indicators are independent, each with probability (c−1)/c for c colours.
196tiles on the board
21.7moves the route forces, on average
24the floor reaches this one board in ten
27tiles on the shortest route across
16.7%chance two neighbours already match
61neighbouring pairs that start matched
Not on this bench: no board, no tiles to tap, no flooding and no solving. It never looks at an actual grid. And the floor it works out is only a floor — the true best is usually higher, and finding it is genuinely hard: deciding the optimal number of moves in a flood game of this kind was proved NP-hard for three or more colours by Arthur, Clifford, Jalsenius, Montanaro and Sach in 2010. That is why a level can promise a budget and still make you work for it.