How to play Gridlight
Gridlight is a daily deduction puzzle on a square grid. Every row and column carries a list of numbers giving the runs of filled squares in that line, in order — a row clued “3 1” has a block of three, at least one gap, then a single. Nothing is hidden and nothing is random: the clues are printed on the board, and from them alone the filled squares can be worked out. The daily grid grows through the week, from 5×5 early on to 10×10 at the weekend, and practice deals any size on demand. There is no timer and no fail state — filling a square that should be blank is counted and named, but the puzzle waits for you either way, and fewer mistakes simply score higher.
How to play
- The numbers along each row and column tell you the runs of filled squares in that line, in order. A row clued “3 1” has three filled squares, at least one gap, then one more.
- Tap a square once to fill it, again to mark it as definitely blank, and a third time to clear it. The marks are just your own notes — they never count for or against you.
- Work a line at a time and use what a full line forces on the lines crossing it. Every puzzle can be finished by reasoning alone; you never have to guess.
- Filling a square that should be blank counts a mistake and tells you so, but nothing ends the puzzle — finish it however many it takes. Fewer mistakes score higher.
- The daily grid grows through the week: 5×5 early on, 10×10 at the weekend. Practice deals any size on demand.
- With a keyboard: arrows move around the grid and Space cycles the square under the cursor.
Tips & strategy
- Start with the lines that are nearly forced. In a 10-wide row, a clue of 8 leaves only three placements — and the middle six squares are filled in all of them, so they are certain before you have decided anything.
- A clue whose numbers plus their gaps exactly fill the line is completely determined: “4 5” in a ten-wide row can only sit one way. Fill those first and let them constrain everything crossing them.
- Mark the blanks. Knowing a square is empty is exactly as useful as knowing it is filled, and the marks are what turn a half-solved grid into a forced one.
- When a line stalls, switch axis. The information you need is almost always in the crossing lines, not in the one you are staring at.
- You never need to guess — so if you find yourself about to, there is a deduction still on the board. Every daily is machine-checked to be solvable by reasoning alone before it is dealt.
Accessibility
The grid is a real table with the clues as row and column headers, so a screen reader announces the clue along with the position as you move — "row 3, clue 2 1". Every square is a button that names its coordinates and its state in words ("row 2, column 4, filled"), and filled and marked squares carry a visible glyph as well as a fill, so none of the three states depends on colour. Arrow keys walk the grid as a single tab stop and Space cycles a square, and a "board in words" section lists every row and column clue for play without seeing the grid at all. One polite live region reports mistakes and the solve, not every square.