Firefly Fields Glossary: Star Battle Terms and Definitions

The board

Grid: The whole puzzle: 64 cells in eight rows and eight columns. Also called the board or the field.
Cell: One square of the grid. It ends up holding a firefly or nothing. Also called a square.
Row: A horizontal line of eight cells. Every row holds exactly one firefly.
Column: A vertical line of eight cells. Every column holds exactly one firefly.
Line: A row or a column, when a statement is true of both.
Meadow: LarkSpark’s name for a region: a group of connected cells in one color. There are eight meadows of varying size and shape, and each holds exactly one firefly.
Region: The general puzzle word for a meadow. On paper, regions are usually marked with heavy outlines and no color.
Container: Any row, column or region: a group of cells that must hold a set number of pieces. The word comes from Krazydad’s tutorials.
Neighbor: A cell that touches another along a side or at a corner. A cell in the middle of the grid has eight neighbors, an edge cell has five and a corner cell has three.

Firefly: The piece you place in Firefly Fields. A finished board has eight, one in every row, column and meadow, with no two touching.
Star: What a firefly is called in a Star Battle. The rules for placing it are the same.
Queen: What the piece is called in one-star puzzles that borrow the chess piece. Unlike a chess queen, it only rules out the cells it touches, plus its row, column and region.
Cross (×): The mark for a cell that can’t hold a firefly. In Firefly Fields a second click on a cell, or a right-click, sets it.
Candidate: A cell that could still hold the firefly for its row, column or meadow, because nothing has ruled it out yet.
Elimination: Ruling a cell out and marking it ×. Most of the solving is elimination, and the fireflies go in the cells that are left.
Forced firefly: A firefly that must go in a cell because it is the last candidate in its row, column or meadow.
No-touching rule: The rule that two fireflies can’t be neighbors, even diagonally. Placing a firefly rules out every cell around it.

Star Battle: The puzzle type Firefly Fields belongs to, created by Hans Eendebak for the 2003 World Puzzle Championship. Every row, column and region holds the same number of stars, and no two stars touch.
One-star puzzle: A Star Battle with a single star in each row, column and region. It is the easiest form and is usually played on a small grid such as 8×8.
Two Not Touch: The name under which The New York Times has printed two-star Star Battle puzzles since 2020.
Eight queens problem: A chess problem first published in 1848: place eight queens on a chessboard so that none can capture another. It has ninety-two solutions and no regions.
Object placement: The family of logic puzzles in which you decide which cells hold an object, such as a star, a ship or a tent. Star Battle is one of them.
Unique solution: A puzzle with exactly one correct answer. A well-made Star Battle has a unique solution that can be reached by logic.

Smallest meadow first: The usual way in: start with the meadows that have the fewest cells, because they have the fewest choices. A meadow of one cell has its firefly already.
Confined meadow: A meadow that sits entirely inside one row or one column. Its firefly must be in that line, so every other cell of the line is empty.
Two-by-two rule: Any two-by-two block of cells holds at most one firefly, because every pair of cells in it touches. Krazydad’s tutorials call it the four-squares rule.
Counting rows against meadows: When a number of meadows fit entirely inside the same number of rows or columns, those meadows take all the fireflies for those lines, and every other cell in the lines is empty.
Testing a cell: Checking what a firefly in a cell would do. If it would leave some row, column or meadow with no candidate, the cell must be empty. Krazydad’s tutorials call this crowding.
Mini region: The few candidates left in a row, column or meadow once the rest are crossed out. One of them holds the firefly, so any outside cell that touches all of them is empty.