Tango is a balance puzzle — fill every cell with a sun or a moon so each row and column has equal counts, avoid three identical symbols in a row, and satisfy equal (=) and opposite (×) signs between neighbors. This guide covers the constraint-reading and pattern techniques that make Tango boards click.

## The three rules in practice

1. **Equal counts** — on an 8×8 grid, each row and column needs four suns and four moons (grid size varies; counts are always half and half).
2. **No three in a row** — horizontally or vertically, you cannot place ☀️☀️☀️ or 🌙🌙🌙.
3. **Sign constraints** — `=` means adjacent cells match; `×` means they differ.

Rules 2 and 3 interact constantly. An equal sign between two cells often forces a chain of matching symbols — and that chain can trigger the no-three rule if it grows too long.

## Read signs before filling

Before placing symbols, scan all visible signs:

| Sign | Meaning | Deduction |
|------|---------|-----------|
| `=` | Same symbol | If one side is sun, the other is sun |
| `×` | Opposite | If one side is sun, the other is moon |

When a cell is empty but its neighbor is filled, the sign tells you what the empty cell must be. Work these forced placements first.

## The no-three rule creates forced opposites

If a row has ☀️☀️ with an empty cell on either end, that empty cell **must** be 🌙 — otherwise you would get three suns.

Similarly, ☀️_☀️ (sun, empty, sun) forces the middle cell to moon.

Scan for these patterns after every placement. They are the Tango equivalent of sudoku's "naked single."

## Balance counting

Track sun/moon counts per row and column mentally (or on paper):

- If a row already has four suns, every remaining empty cell in that row must be moon.
- If a row has three suns and one empty, that empty cell must be moon to avoid a fourth sun.

Balance counting becomes critical in the last third of the grid when few empty cells remain.

## Equal chains

Two cells linked by `=` form a chain. If one is known, the other matches.

Watch for chains that approach length three — an `=` chain of three identical symbols violates the no-three rule. When a chain would force three in a row, one of the chain links must break — which means the adjacent non-chain cells must be the opposite symbol.

## Opposite pairs and balance

A `×` sign guarantees one sun and one moon. Use these to fix balance:

- In a row missing one sun and one moon with a `×` pair still empty, the pair must be one of each.
- If the row already has excess suns, the `×` pair must be moon-sun (with moon on the side that still needs moons).

## Prefilled cells are anchors

Many Tango boards start with locked cells. Build outward from these:

1. Apply sign constraints from each given.
2. Run no-three scans on adjacent rows and columns.
3. Update balance counts.

## Common mistakes

- **Ignoring vertical no-three** — players check horizontal runs but miss vertical triples.
- **Forgetting balance** — a placement that satisfies signs may break the equal-count rule.
- **Filling too fast** — one wrong symbol early cascades into many conflicts.

## Practice path

| Step | Link |
|------|------|
| Rules | [Tango how-to-play](/tango/how-to-play) |
| Demo | [Tango demo](/tango/demo) |
| Strategy practice | [Random Tango](/tango/random) |
| Dailies | [Tango archive](/tango/archive) |

Tango rewards patience with signs. Slow down on the first pass, mark forced cells, then accelerate as the grid fills.