Tangram Fit

A shape is cut out of a five-by-five lattice — thirteen to fifteen cells, never the whole square — and four to six flat pieces have to cover it with nothing left over and nothing poking out. The pieces come from the same eight shapes every round: a domino, a stack, a bar, a post, an L, a J, a 2 by 2 block and a T. They never turn and never flip, so the shape you see in the rack is the shape that fits, and what you learn about where a J can go is still true in the next puzzle. Every outline is built by laying pieces down first and then checking, before you ever see it, that no second arrangement covers it — so an answer definitely exists, and there is only the one.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Focus the board — click it, or press Tab until it is focused.
2. Read the outline. Solid cells are part of the shape you have to cover. The dashed, empty ones are holes in the lattice: nothing goes there, and pressing on one wastes a move.
3. Look at the rack. Each piece is drawn as a miniature of its own outline, with a glyph beside it and its cell count underneath. The one you are holding is ringed.
4. Press Shift to hold the next piece in the rack. Picking a piece up is free.
5. Move around the lattice with the arrow keys. A dashed outline shows exactly where the held piece would land, and it carries a ✕ when that landing is illegal — so you can check before you commit.
6. Press Enter to put it down. The cell under the cursor is where the piece's own first cell goes — its top-left-most one — and the rest of the piece follows from there.
7. Press Enter on a cell a piece already covers to take it back out, or press Esc, or click its entry in the rack. A pointer does the same job: click a cell to drop, click a covered cell to lift.
8. Watch the moves. Every press of Enter costs exactly one move, whether it places a piece, takes one back or bounces. A flawless run spends one move per piece; the rest of the budget is your room to be wrong.
9. Cover every cell of the outline before the moves run out.

How do you work out which piece covers each part of a silhouette?

Work from the most awkward cell, never from the biggest piece. Find the first uncovered cell reading left to right and top to bottom: whichever piece ends up covering it must have its own first cell sitting exactly there, because a piece's first cell is its top-left-most one and there is nothing above or to the left of that gap still to cover. On an irregular outline that usually leaves one or two candidates instead of thirty — and the notches and corners of the shape cut the list down further, because most pieces would poke straight out of them. Cover that cell, then look for the next uncovered one and repeat. The outline unwinds almost without a choice. The habit that costs people the round is the opposite one: dropping the four-cell T somewhere roomy because it feels productive, then finding that the notch in the corner can only take a domino you have already spent.

Is every outline guaranteed to have exactly one answer?

Yes, and both halves are settled before it is dealt. The outline is not drawn and then filled — the pieces are laid down first, each one touching what is already there, and the outline is simply whatever they covered. So a covering exists by construction: it is the arrangement we just made. Then a search covers the outline every way the pieces allow, counting to two and stopping. If it finds a second arrangement the outline is thrown away and another is built. Two identical pieces swapping places is not counted as a second answer, because once they are down you could not tell which was which.

Why can't the pieces be rotated or flipped?

Because turning pieces is dexterity, not thought. Once a piece can appear in eight orientations, the game becomes trying them all by hand, and any cell you are stuck on has too many candidates to reason about. Fixing the orientation means each piece has only a handful of legal seats, which is what makes "which piece covers this gap?" a question with an answer you can work out. It also means the whole game plays from the keyboard, with no rotate-and-flip gesture to invent, and it keeps the puzzle small enough to verify exhaustively before you see it. The side effect is the best part: because the same eight shapes come back every round, they stop being obstacles and start being tools.

Where does the move budget come from?

From the verifier, not from a guess. The floor is one move per piece — what a run with no mistakes spends. On top of that comes a fixed allowance plus extra moves in proportion to the number of dead ends the uniqueness search hit: placements that are perfectly legal, look reasonable, and lead nowhere. Those are exactly the mistakes a thinking player makes, so an outline that admits a lot of them hands you more room, and one whose cells are nearly all forced hands you less. The budget is therefore always achievable and always tight enough that dropping pieces at random loses.

Is there any money, betting or in-app purchase in this?

None, and there never will be. No currency, nothing to buy, no lives to refill, no prize of any kind at the end. The score is a number derived from the outline you covered and the moves you had left, and it stays on your device.

Does it work offline?

Yes. Once the page has loaded once, the whole game is on your device — the shapes, the builder, the verifier, all of it. No outline is ever fetched and no server is involved in play at any point.

Can I play it with a keyboard or a screen reader?

Both. Arrows move around the lattice, Shift changes which piece you hold, Enter commits and Esc takes back. Nothing is carried by colour: a placed piece is drawn as one joined outline, it repeats its own glyph in every cell it owns, and every piece is announced in words — "3 squares in a J" — along with whether it is in the rack or on the board. Each cell of the lattice announces whether it is outside the outline, open, or covered and by which piece. The board publishes a full parallel description, so the game is playable without seeing it at all.

A five-by-five lattice, an outline of thirteen to fifteen cells, and four to six pieces of two, three or four cells each. That is deliberately small: the uniqueness check is exhaustive rather than sampled, and it has to finish instantly on a phone. Pieces are fixed in the one orientation the catalogue lists them in, and a shape made of squares joined edge to edge is called a polyomino if you want to read further. Outlines that could be covered two different ways are discarded rather than shipped, so you will never meet one. Losing reveals the answer on the board.

Block Fit is the same family of reasoning against a full rectangle rather than a cut-out shape, with the pieces re-cut every deal instead of drawn from a fixed set. Shadow Match and Grid Paint are the other spatial puzzles here — one rebuilds a solid from its silhouettes, the other asks for a single unbroken path. Fence Loop and Light Grid derive their move budgets from their own solvers the way this one does, so tight is always achievable.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.