Shrooms

Forage two edible mushrooms in every row, column, and dirt patch — none of them touching, not even diagonally. Mark safe squares with grass, and avoid poisonous mushrooms!
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From the desk

Notes on Shrooms

Where Shrooms comes from

Shrooms wears a forest costume, but underneath it is a Star Battle — one of the youngest classics in the logic-puzzle canon. Star Battle came out of the competitive puzzle world, first appearing at the World Puzzle Championship in the early 2000s, credited to the Dutch puzzlemaker Hans Eendebak. Where Sudoku descends from a 1979 magazine page, Star Battle was built for championship solvers from the start: a grid carved into irregular regions, a fixed number of stars per row, column, and region, and the rule that gives the genre its bite — no two stars may touch, even diagonally. The two-star variant, which Shrooms uses, is the one that broke into the mainstream; American solvers may know it as Two Not Touch, printed in the New York Times since 2019. Shrooms trades stars for mushroom caps and austerity for soft color, but the deductive machinery is the championship article, unchanged: every board has one solution, and logic alone will take you there.

How to get better at Shrooms

Treat every placed mushroom as a small explosion. The no-touch rule clears all eight surrounding squares the instant a cap goes down, so mark that ring with grass immediately. Half of good Star Battle play is bookkeeping — the solvers who fall behind are the ones who make the same elimination twice.

Start where the board has the least freedom. A region squeezed into a narrow strip or a tight pocket may have only one or two legal ways to seat its pair of mushrooms, and whatever those arrangements share is certain. If both options put a mushroom in the same square, plant it; if both leave a square empty, grass it. You can bank deductions without committing to either arrangement.

Count rows against regions. If two regions live entirely inside the same two rows, those regions must supply all four of the rows' mushrooms — so every other square in those two rows is grass, wherever its region sprawls. This counting argument, run in both directions, is the deepest well in the game, and on the 12×12 it is where most of the solve lives.

Think in two-by-two blocks. The touch rule means any 2×2 area holds at most one mushroom. A row of eight is four such blocks, and it needs two caps — so when a stretch of row collapses to a single pair of blocks, the spacing does the placing for you.

Match the tool to the size. On the 8×8 you can hold the logic in your head; on the 10×10 and 12×12, grass early and often, and lean on candidate marks when two arrangements are still live. The hint will name a next step when you stall, but the counting arguments above are almost always what it would tell you.

A round in the life

Easy board, 8×8, two minutes in. A stubby region sits against the left edge, six squares in a 2×3 pocket. Two mushrooms must fit inside it, and the touch rule leaves exactly two seatings — and both of them use the pocket's top-left square. You plant the cap. Grass blooms across its diagonal shadow, and the square below, freshly blocked, forces the region's second mushroom into the bottom-right corner of the pocket. Now the ledger: that column just received its second cap, so the whole column goes to grass — which starves the neighboring region down to one legal pair. Three moves, no guesses, and the board has begun to fold in on itself, exactly the way it was built to.

Good to know

Questions about Shrooms

Exactly two mushrooms in every row, every column, and every color region (the dirt patches), with no two mushrooms touching — not even diagonally. Get all 2N down with no rule broken and the day is foraged clean.
A red, poisonous mushroom means it breaks a rule right now: there are more than two in its row, column, or region, or it’s touching another mushroom (including diagonally). A safe mushroom shows a blue cap. An under-filled line isn’t an error — you’re just not done.
Grass is your own “no mushroom here” mark — a way to rule a square out as you reason. Tap a cell to cycle it empty → grass → mushroom → empty. Grass is never required and never scored; it’s just an aid.
Check tells you whether the board holds any errors — a mushroom sitting somewhere it can’t belong in the real solution. It reports how many are wrong, never which ones, so it nudges without spoiling.
A hint only highlights and explains one logical step — a misplaced mushroom, squares blocked next to a mushroom, or a region a mushroom would starve. It never places anything for you. Hints don’t affect your score or streak; they’re just tallied in your shared result.
No — Easy (8×8), Medium (10×10), and Hard (12×12) are separate puzzles sharing the day, each timed independently. Switch with the difficulty control above the board.

Still stuck? .

From the rulebookHow to play Shrooms

A forest grid in colored regions. Find where the mushrooms grow.

  • Grow exactly two mushrooms in every row, every column, and every color region.
  • No two mushrooms may touch — not even diagonally.
  • Tap a cell to cycle it: empty → grass (your “no mushroom here” mark) → mushroom → empty.
  • A safe mushroom shows a blue cap. One that breaks a rule turns red & poisonous, flagged with “!”.
  • Pick a size — Easy 8×8, Medium 10×10, Hard 12×12 — each is its own daily puzzle, timed independently.
Pieces

A safe mushroom — no rule broken so far.

A poisonous mushroom — too many in its row, column, or region, or touching another.

Grass — your own marker for “nothing grows here.”

Stuck? Hint points out one logical step — a misplaced mushroom, cells blocked next to a mushroom, or a square that would starve its region. It only highlights and explains; it never places a mushroom and never counts against you.