How to play Tents & Trees The three rules, then the deductions that actually solve a board without guessing.
Tents & Trees takes about thirty seconds to learn and considerably longer to get good at. The rules below are the whole game. Everything after them is technique: the specific arguments that turn a board you are stuck on into a board you have finished, without ever resorting to trying something to see what happens.
Give every tree one tent in a square directly beside it. Never let two tents touch, not even at a corner. Make each row and column hold exactly the number of tents printed beside it. Every puzzle has one solution and can be reached by deduction alone.
The three rules
1. One tent per tree
Every tree has exactly one tent in a square directly beside it: up, down, left or right. Never diagonally. The pairing runs both ways: each tent belongs to exactly one tree, so a solved board always has as many tents as it has trees.
A tent is allowed to sit next to several trees. It still only counts for one of them. This is the source of most of the interesting deductions in the game.
2. Tents never touch
No two tents may share an edge or a corner. Once a tent is placed, all eight squares around it are settled: none of them can hold another tent. Trees have no such restriction and may sit against each other freely.
3. Match the numbers
The number beside each row and column is how many tents that line holds. Exactly that many, not at least that many. A line numbered zero contains no tents at all.
Grass is how you actually solve it
Beginners tend to hunt for the next tent. Strong solvers do the opposite: they spend most of their time marking squares as grass, meaning “no tent here”.
Grass costs nothing, is never penalised, and is the only way to make progress visible. Almost every deduction in this game is really an elimination, and eliminations are invisible unless you write them down. A board covered in grass is a board that is nearly solved; a board with three tents and no grass on it is a board you are about to get stuck on.
The opening: two moves that need no thought
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Grass every square with no tree beside it
A tent has to be directly beside a tree, so any square with no tree above, below, left or right of it can never hold one. A tree at a diagonal does not count. This single sweep usually clears a third of the board or more, and it is always safe.
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Fill in every zero line
A row or column labelled zero holds no tents, so all of it is grass. Do these immediately. Zero lines frequently strand a nearby tree with only one square left, which hands you your first tent for free.
The deductions
These are the arguments the game's own solver uses, in roughly the order they become necessary. Every board in Tents & Trees can be finished with them.
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Only one spot left
Find a tree with exactly one free square still beside it. That square is its tent, because it has nowhere else to go. Place it, then immediately grass all eight squares around it, which often triggers the same deduction on a neighbouring tree.
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The line is exactly full
If a row or column still needs n tents and has exactly n free squares left, every one of those squares is a tent. The mirror case is just as useful: once a line already holds all the tents its number allows, everything else in it is grass.
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Nobody needs this square
A free square only matters if some unpaired tree could still use it. If every tree touching a square is already provably paired with a tent of its own, then that square serves no one, and it is grass. This is the deduction most people miss, and it is often the one that unblocks a stalled board.
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Spacing forces the issue
Tents need room, because they cannot sit next to each other. Sometimes a line's number simply cannot fit into the squares that remain unless one particular square holds a tent. Sometimes the reverse: putting a tent in one square would leave the rest of the line unable to fit its count without two tents touching, which rules that square out.
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Competing trees
This is the strongest ordinary technique, and the one that cracks hard boards. Take a group of unpaired trees and collect every free square that any of them could use. If that group has as many trees as the group has available squares, then all of those squares must be tents, because there is no other way to satisfy all of the trees at once.
The same argument works in reverse and is easy to overlook: if those squares are entirely committed to that group of trees, no tree from outside the group can take one of them.
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Assume, and find the contradiction
When nothing else moves, take a single square, suppose it holds a tent, and push the consequences through the rules above. If that assumption forces a line to overflow its number, starves a tree of every square it had, or makes two tents touch, then the assumption was wrong and the square is grass. The same works the other way round.
This is still deduction rather than guessing: you are not trying a branch and hoping, you are proving one option impossible and keeping the other.
Controls in the app
- Tap to cycle. A tap steps a square through grass, then a tent, then back to empty. The order is a setting if you would rather reach the tent first.
- Long-press for a tent. One move, cycling the opposite way.
- Drag to sweep grass. Press and drag across empty squares to grass all of them at once.
- Tap a finished number. Once a line has all its tents, tap its number to flood the rest of that line with grass.
- Pinch to zoom, two fingers to pan on the larger boards.
Questions
Can two tents be diagonally adjacent?
No. Tents may not touch in any of the eight directions, so a corner counts as touching. Trees have no such rule and may sit against each other freely.
Can one tent belong to two trees?
No. The pairing is one to one: each tree gets its own tent, and each tent is counted for exactly one tree. A tent may be physically adjacent to several trees, but it only ever serves one, which is why a solved board has exactly as many tents as trees.
What is the best first move?
Grass every square that has no tree directly beside it, then fill in any line numbered zero. Neither needs any thought, both are always safe, and together they usually shrink the board enough to leave some tree with only one square left.
Is this the same as Sudoku or a nonogram?
No, though it appeals to the same solvers. Like a nonogram it puts numbers along the edges of a grid, and like Sudoku it is solved by elimination toward a single guaranteed answer. What is different is the pairing rule. Matching each tree to its own tent brings in spacing and competition arguments that neither of the others has.
I am stuck and I think I have to guess.
You do not. Every board in the game is checked before it ships to confirm it can be finished by the techniques on this page, and that it has only one solution. Being stuck means a deduction is available that has not been spotted yet, most often the “nobody needs this square” one, or a group of trees competing for the same set of squares.
Play it
Tents & Trees is free on Google Play, works entirely offline, and has an interactive tutorial that walks through the opening moves on a real board.