How we make puzzles

Every Gridaday puzzle is made by our own code and checked by more code before anyone sees it. Nothing is copied from other sites or books. This page explains the three steps, generate, check, grade, and lists what is in the bank.

1. Generate

Each genre has its own generator. Star Battle places stars first and grows regions around them; Takuzu fills a valid grid and removes circles; Killer Sudoku and Kakuro fill digits and draw cages or runs; Skyscrapers starts from a Latin square and removes clues. Nonogram pictures are drawn from the Noto Emoji set (Apache License 2.0) and turned into grids of 10x10 to 20x20. Each daily puzzle comes from a seed made of the genre, the date and the level (nonogram pictures from a fixed order of the emoji set), so running the generator again gives the same puzzle.

2. Check: exactly one solution

A puzzle ships only if a separate counting program, which shares no code with the generator or the solver, searches for a second solution and finds none, and finds the same solution we store. Every puzzle in the bank has passed it, and the build checks it again whenever a puzzle or the checking code changes.

3. Grade: the hardest technique

Our solver works like a careful person: it always takes the simplest technique that makes progress, and starts again from the simplest after every step. The level is the highest tier it needed. In most genres the last tier is contradiction (assume, follow the rules, find a dead end), and needing it makes a puzzle Expert; nonograms stay line by line, and there Expert means full line analysis or the forcing technique on ten lines or more. The same solver gives the hints, so a hint never uses a technique harder than the puzzle's level. The tiers:

Genre	Tier 1	Tier 2	Tier 3	Tier 4	Tier 5
Star Battle	Stars never touch, Full row, column or region, Last cells left	Region inside one line, A star here leaves no room	N regions in N lines, 2x2 blocks, Two-line squeeze, Short chain	Contradiction
Takuzu	Pairs, Sandwich	Balance	Line analysis	No twin lines	Contradiction
Nonogram	Simple boxes, Finished lines	Spaces split the line, Simple spaces	Forcing from known cells, Out of reach	Full line analysis
Kakuro	Unique sums, Last cell of a run, Naked single, Combination intersection	One place left, Naked pair	Full run analysis	Contradiction
Killer Sudoku	Cage combinations, Naked single, Hidden single	Rule of 45, Naked pair, Cage inside a house	Rule of 45 on several houses, Hidden pair, Naked triple	Contradiction
Skyscrapers	Clues 1 and N, Naked single, Hidden single	Distance from the clue, Naked pair	Line permutations	Contradiction

The bank

Genre	Daily puzzles	Dates	Unlimited pool	All
Star Battle	2,560	16 October 2026 to 10 March 2028	550	3,110
Takuzu	2,048	16 October 2026 to 10 March 2028	700	2,748
Nonogram	2,048	16 October 2026 to 10 March 2028	500	2,548
Kakuro	2,048	16 October 2026 to 10 March 2028	550	2,598
Killer Sudoku	2,048	16 October 2026 to 10 March 2028	350	2,398
Skyscrapers	2,048	16 October 2026 to 10 March 2028	550	2,598

Source: the Gridaday bank as built on 2026-10-17.

Dailies change at midnight in your own time zone; daily number 1 is 21 October 2026.

Who does what

The generators, solvers, checks and these pages were written with an AI coding assistant, directed and reviewed by BiLingoPlus LLC; every rule a solver uses is listed on the techniques pages, and every number on the site is computed from the bank, not typed. Automated checks read the finished site before each release: they confirm the single solutions, re-grade every puzzle, check that each technique share printed on a page matches the bank, and test the game on a phone-sized screen.

If something is wrong

Every puzzle has a hint that explains its next step, so a mistake in a puzzle shows quickly. If you find one, write to hello@gridaday.com; fixes are listed on the corrections page.