A Dominosa daily puzzle is a compact 2-by-3 logic board with six numbered tiles that you must partition into three orthogonally adjacent dominoes, each using a different unordered number pair. On the standard daily board the first row reads 0 0 1 and the second row reads 1 2 2, so the clean solution pairs the three vertical columns into 0-1, 0-2, and 1-2. Each pair covers two cells, the three pairs cover all six cells, and no unordered value appears twice. A daily run aims for exactly 1,200 points because three accepted dominoes at 400 points each produce that total. Two invalid selections, or a board remainder that no longer has a valid completion, ends the run before you reach 1,200. Players who want one small logical tiling puzzle a day will find that the entire game state fits in six cells, that every rule is auditable, and that a successful run can be replayed mentally without a recorded board. The disclosed fixture is identical for every player, which makes the daily puzzle a shared reference point rather than a randomly seeded challenge.
The game is built for keyboard control and short sessions so that every action, including selection, cancellation, Restart, and the shared Boss Key, is reachable without a mouse. Dominosa sits on a small semantic grid that uses only surface, foreground, line, accent, and danger tokens, which means it inherits the surrounding site's color rules rather than overlaying its own canvas. There is no random generator, no upload, no account, no hardware permission, no audio, no download, and no network request. Every daily board is the disclosed teaching fixture, and the best score stays in the browser's local storage. For a player who wants one small logical tiling puzzle a day, the format is deliberately minimal so the rule surface stays the focus.
The 2-by-3 Daily Board and What Counts as a Domino
The Dominosa daily puzzle is fixed: a 2-by-3 array of cells holding six visible digits. A domino is exactly two orthogonally adjacent cells, so it always shares an edge, never a diagonal. Cover the whole six-cell board with three dominoes, and each digit must belong to exactly one of those three. Pair order does not matter, which is the rule that turns the game from a positioning puzzle into a uniqueness puzzle. A 0-2 domino and a 2-0 domino are treated as the same unordered value pair and may appear only once across the entire board, a constraint that is covered in more depth in the pair-repetition guide.
On the disclosed board the row layout reads 0 0 1 on top and 1 2 2 on the bottom. The vertical-column tiling pairs the left column as 0-1, the middle column as 0-2, and the right column as 1-2. These three unordered pairs are distinct, they cover every cell exactly once, and no row needs a horizontal placement. The full vertical-column solution is a teaching example rather than a restriction, because larger Dominosa puzzles use the same pair-uniqueness reasoning but on different shapes. The same shape rules also explain why the diagonal-tile rule is enforced: adjacency is the legal move, not proximity.
How to Play a Dominosa Daily Puzzle
- Move the outlined cursor with the arrow keys to land on your first tile, then press Space or Enter to anchor it.
- Arrow-key to an orthogonally adjacent uncovered tile and press Space or Enter again to form a domino with the anchored cell.
- Cover all six cells with three different unordered number pairs before two invalid selections or an unsolvable remainder ends the run.
- Press Restart to clear every domino, every selection, every mistake, and every point so you can retry the same board from scratch.
- Double-press Escape to swap the board for the spreadsheet-style Boss Key view, then double-press Escape again to restore the unchanged board.
The same flow works for mouse and touch players: each cell is a semantic button, so clicking or tapping the anchored tile again cancels it, and already covered tiles are visually disabled and cannot be reused. The outlined cursor always shows where the next anchor will land, which is useful on a board this small because a stray arrow press can move you off the intended tile in a single step. Once the first domino is anchored, the second anchor must be a horizontal or vertical neighbor of that cell, not a diagonal one.
Why Unordered Pairs Make or Break a Run
The Dominosa rule that catches most beginners is the unordered-pair constraint. A 1-2 domino and a 2-1 domino look like different pairs on paper but are treated as one pair inside the solver. That constraint is the game's deepest resource: you cannot simply chase visually obvious pairs because two visually identical pairs would still count as a single repeat. The exhaustive completion search after every accepted domino relies on this sorted value-pair key to prune the search space and to flag a run that no longer has a legal finish.
Pair uniqueness also changes how a horizontal opening behaves. A tempting horizontal 0-0 across the top-left cell looks fine in isolation, but the rest of the board can no longer be tiled with three distinct unordered pairs, so the recursive solver marks the run as deadlocked immediately. That early signal prevents a board that looks active but cannot actually finish, which is a common failure mode in pair-based tiling games. On the disclosed teaching board the vertical-column tiling side-steps that trap because each vertical pair uses a different unordered value, which keeps the remaining columns available for two more distinct pairs.
Reading the 1,200-Point Score
Dominosa rewards a clean run with exact arithmetic: each accepted domino adds 400 points, so three accepted dominoes produce exactly 1,200 points. The score is intentionally exact so a player can audit any claimed run without ambiguity. The exact figures come from the tool itself, so the table below describes the relationship rather than recomputing the math.
| Milestone | Accepted dominoes | Score |
|---|---|---|
| First domino placed | 1 | 400 |
| Second domino placed | 2 | 800 |
| Perfect daily run | 3 | 1,200 |
| Run interrupted by two mistakes | 0 to 2 | Score frozen at interruption |
An invalid selection does not award points and instead counts as a mistake. A second invalid selection creates a terminal failure state, which means the run freezes at whatever score you had reached. Restart clears every domino, every selection, every mistake, and every point, so a player who notices a bad opening can reset and try again on the same disclosed board. The best score survives a Restart because it lives in local browser storage rather than in the active run state.
How the Deadlock Detector Protects a Run
After every accepted domino, Dominosa runs an exhaustive completion search on the uncovered cells. The search looks at the first uncovered tile, tries every uncovered orthogonal neighbor whose unordered value pair is still unused, and recursively checks whether the remainder can be tiled. If no perfect unique-pair tiling remains, the run is marked deadlocked immediately. The check runs on the same state the interface uses, so what the player sees on the grid is what the solver tests, rather than a parallel simplified copy.
That real-time check matters for daily practice because pair-uniqueness dead ends are easy to create accidentally. A horizontal pair that looks reasonable can leave the two remaining columns without a valid completion, and a player without a deadlock detector would only discover the failure after placing two more rejected attempts. The isolated test in the tool confirms that the empty board has a completion, that a tempting horizontal 0-0 opening has none, that the three-column winning tiling succeeds, that the result equals 1,200 points, and that two invalid nonadjacent choices trigger terminal freezing. A separate cursor-movement test confirms that the arrow keys reach every cell.
Keyboard, Mouse, and Touch on a Six-Cell Board
Because the daily board is only six cells, control choice matters less than on a larger grid but still affects pace. Keyboard players move the cursor one cell at a time, anchor with Space or Enter, and cancel by re-anchoring the same cell. Mouse and touch players can select the same visible cells without a keyboard, which is helpful on touch devices where arrow-key clusters are missing. The grid uses semantic buttons and CSS grid rather than a canvas, so accessibility tools see real controls rather than pixel regions.
| Input method | Move cursor | Anchor tile | Cancel anchor | Best for |
|---|---|---|---|---|
| Keyboard | Arrow keys | Space or Enter | Re-anchor the same tile | Fast daily runs without leaving the home row |
| Mouse | Click an adjacent cell | Click a tile | Click the anchored tile again | Players who prefer pointer control on small boards |
| Touch | Tap an adjacent cell | Tap a tile | Tap the anchored tile again | Phones and tablets where arrow keys are missing |
Already covered tiles are disabled, so the input method does not change which cells can be selected at any moment. That consistency is what lets the recursive solver and the visible grid stay in lockstep across keyboards, mice, and touchscreens.
Building a Daily Dominosa Habit
A useful solving habit before any domino is to list the unordered pairs already used and then inspect the constrained edge cells before committing. On the disclosed teaching board, vertical pairs expose the core rule cleanly because each column gives a distinct unordered pair. Larger Dominosa puzzles follow the same reasoning, but with more rows and more columns, so the habit transfers directly: uniqueness still dominates, and coverage alone is insufficient when a duplicated pair would violate the rule.
For players who want to extend the daily habit into related compact logic puzzles, the same site offers a few natural next steps. Numberlink shares the orthogonal-path theme and rewards careful pair planning, and Hashi Bridges asks for a connected network with matching island clues across a small six-island fixture. None of them share the 1,200-point scale, but the underlying habit of stating the constraints you have already committed to before testing the next move is the same habit a Dominosa daily run rewards. Pair that habit with the Boss Key for shared screens, keep the best score in your browser's local storage, and the disclosed 2-by-3 board becomes a small but reliable daily logic workout.