Clear Shot Glossary: Arrow Puzzle Terms and Definitions

The board and its arrows

Board: The grid the puzzle is played on: 20 rows and 20 columns, almost entirely covered by arrows.
Square: One cell of the board. Every square is either empty or part of exactly one arrow.
Edge: One of the four sides of the board. Arrows leave across an edge. The squares along the edges are called the border or the rim.
Arrow: A piece made of a shaft with a head on one end. It covers at least two squares and never overlaps or crosses another arrow.
Head: The pointed end of an arrow. The head alone decides which way the arrow flies: up, down, left or right.
Shaft: The body of an arrow, running from square to square in straight pieces. Its shape has no effect on where the arrow goes.
Tail: The end of the shaft farthest from the head. A tail blocks other arrows just as well as any other part does.
Bend: A corner where the shaft turns. An arrow can have any number of bends, and it follows them on its way out.
Long arrow: An arrow that covers many squares. It lies across many lines, so removing one often frees several others.

Line of flight: The straight run of squares from an arrow’s head to the edge it points at. Also called its path or its line.
Free arrow: An arrow whose line of flight is completely empty, so it can leave now. An arrow with its head on the edge, pointing outward, is always free.
Blocked arrow: An arrow with any part of another arrow in its line of flight. It can’t leave until that line is empty.
Blocker: An arrow that lies in another arrow’s line of flight. A blocker can sit anywhere along the line, even at the far side of the board.
Shot: Tapping a free arrow so that it flies off the board, head first. The squares it covered are empty from then on.
Opening: The gap left where an arrow has just been removed. Arrows aimed across those squares are the likeliest to have become free.
Stand-off: Two arrows aimed straight at each other along one line. Neither could ever leave, so a real board never contains one. If you think you see one, you’ve misread a row or column.

Daily board: The one board set for a given date. Everyone playing that date gets the same arrows in the same places.
Bump: What happens when you tap a blocked arrow. It runs forward, hits its blocker and returns, five seconds are added to your clock, and the bump is counted on your result.
Hint: A request that lights up one free arrow in green for a moment. It adds no time, but the number of hints you use is kept with your daily record.
Finishing time: The time on the clock when the last arrow leaves, including every bump penalty. It goes on the day’s board with everyone else’s.
Clean solve: A players’ term for a finish with nothing against it on the record: no bumps and no hints.
Streak: The number of days in a row on which you have solved the daily board.

Border sweep: The usual first step: look once around all four edges and shoot every arrow whose head is on the rim pointing outward.
Looking in from the edge: Checking one row or column from the edge inward. If the first thing you meet is a head pointing back at you, that arrow is free. If it is anything else, nothing can leave along that line from that side.
Following the opening: Checking the rows and columns that run through the gap you just made before looking anywhere else. It is faster than rescanning the whole board.

Dependency: The relation between a blocked arrow and its blocker: the first can’t leave until the second has gone. Chains of dependencies explain which arrow is the real obstacle.
Cycle: A ring of dependencies that leads back to its starting arrow. A board with a cycle could never be cleared. A stand-off is the smallest cycle.
Topological order: An order of removal in which every arrow goes after all of its blockers. One exists exactly when there is no cycle, and a board usually has many.
Unblocking puzzle: The wider family of puzzles in which pieces get in each other’s way and the task is to get one or all of them out. Sliding-block puzzles belong to it.
Tap-away puzzle: A phone puzzle in which a tapped piece flies off in its own fixed direction if nothing is in the way. Arrow puzzles such as this one are a flat version, sometimes called arrow escape puzzles.