What kind of puzzle is Tents and Trees?
Tents and Trees is a logic puzzle where you pitch one tent next to every tree, directly up, down, left or right, so that the counts at the ends of the rows and columns all work out. It is also known simply as Tents and sits next to Sudoku in many newspaper puzzle pages and apps.
Here the board is a forest campsite. Conifers stand on a lawn, and tapping a tile raises a colourful A-frame tent that flaps as it goes up. When a tree and a tent are paired a small campfire crackles between them, and once the last tent finds its spot night falls, each tent lights up from inside and stars appear one by one.
What exactly are the rules?
There are four. Every tree is paired with one tent that sits directly beside it, tents may not touch even diagonally, each row and column holds exactly the number of tents shown, and the number of tents equals the number of trees. Only one arrangement on each board satisfies all four.
| Rule | Meaning |
|---|---|
| Pairing | Each tree owns one tent in the tile above, below, left or right of it. Diagonal tiles do not count as beside |
| One to one | A tent cannot belong to two trees. A tent between two trees is the partner of only one of them |
| No touching | None of the eight tiles around a tent may hold another tent. Touching tents turn red |
| Line numbers | The number above a column counts its tents, the number left of a row counts its tents. Too many turns the number red, exactly right turns it green |
| Tiles with no tree | A tile that does not touch a tree up, down, left or right can never hold a tent |
Where do I start? The standard patterns
The classic opening is to grass out every row and column marked 0, grass out every tile that does not touch a tree, and then pitch tents wherever a tree has only one free side left. Tapping a number fills that whole line with grass in one go, so this takes only a few taps.
| Pattern | What follows |
|---|---|
| A row or column marked 0 | The whole line is grass. Clear these first |
| A tile touching no tree | It can be nobody's tent, so it is grass. On big boards this removes a lot of tiles |
| A tree with one free side | That tile is its tent. Corner and edge trees give you this all the time |
| Number equals empty tiles left | Every empty tile in the line is a tent. Conversely, once the line already has its number of tents, the rest is grass |
| Right after pitching a tent | All eight surrounding tiles are grass. Mark them at once so the next deduction shows |
| Three empty tiles in a row, number 2 | Tents cannot touch, so both ends are tents and the middle is grass |
| Two trees facing one empty tile | Even if a tent goes there it serves only one tree. The other tree must have its tent on another side |
Up to the 8×8 Normal board these seven patterns, applied in turn, carry you to the end. The 12×12 Hard board asks once or twice for a count across two lines: if the only empty tiles left in a row are the two sides of one tree and the row number is 1, that tree's tent must be in that row, so the tiles above and below the tree are grass.
How are boards made, and is the answer really unique?
Every board is generated fresh and a solver counts its answers all the way, so only boards with exactly one answer are served. Seeing the same board twice is practically impossible.
Tents are first scattered on an empty board so that none touch, and a tree is planted beside each one to make the pairs: about seven pairs on 6×6, thirteen on 8×8 and twenty nine on 12×12. The tents in each row and column are counted to make the numbers, and the board with only the trees and numbers goes to the solver. It applies the same deductions a person would, backtracks at the branch points, and finds every answer. If there is more than one, the board is thrown away and built again. That is why every board can be finished by reasoning alone with no guessing.
What is the difference between Hint and Check?
Hint pitches one tent for you, while Check only highlights what is wrong so far in red. Both are counted in your result, so it is best to use them only when stuck.
- Hint: if a tent is in the wrong place it removes that tent first; if a tent tile is marked as grass it pitches the tent there. Otherwise it pitches a tent that follows directly from the tents you already have. The tile is outlined in yellow for a moment.
- Check: for two seconds it marks in red any tent that is not in the answer, grass sitting on a tent tile, touching tents, tents that touch no tree, trees whose every side is grass, and lines with too many tents. If nothing is wrong it says so.
- Undo: takes back one move at a time. Filling a line with grass by tapping a number counts as one move and comes back in one step.
Tips for faster solving
- Clear the 0 lines first. One tap on the number grasses the whole line and the board instantly looks lighter.
- Grass the surroundings right after pitching a tent. Clearing those eight tiles keeps leaving neighbouring trees with a single free side.
- Compare each line's number with its empty tiles. Equal means all tents, number already reached means all grass. A number turning green is your signal.
- Look for two trees sharing one tile. One tile serves one tree, so the other tree needs its tent somewhere else.
- Be generous with grass marks. Most of the reasoning in this puzzle is ruling tiles out, not pitching tents.
Controls
- Touch or mouse: each tap on a tile cycles tent, grass, empty. Right click places or clears grass only. Tapping a number at the top or left fills that line's empty tiles with grass.
- Keyboard: arrows or WASD move the cursor, Space or Enter cycles tent and grass, X marks grass, Backspace clears, Z undoes, H hints, C checks.
- Screen: the timer and tent count sit top left, Undo, Hint and Check sit at the bottom, and the speaker at top right mutes the sound.
How do the daily puzzle and records work?
The daily puzzle is one 8×8 board that changes every day and is the same for everyone on that day. It is the easy way to solve the same board as a friend and compare times.
Your best time for each size is saved in this browser and shown on the start screen, and finishing the daily board records that day as done. Share result on the end screen builds a picture card with your time and hint count.
Records stay in this browser only and are never sent to a server. Clearing browser data clears them too.