Nonogram
Fill the grid
The numbers say how many squares in a row are filled, in that order. Click once to fill, twice to mark a square you know is empty, three times to clear it.
How do the numbers work?
Each number is a run of filled squares in that row or column, in the order shown. Two numbers mean two runs with at least one empty square between them. The grid is solved when every run matches.
Click a square once to fill it, twice to mark it as empty, three times to clear it. Marking the empty ones is how you keep track of what you have ruled out.
Are the levels stored somewhere?
No. Each level is built from its own number with a seeded generator, so level 7 is the same grid for everyone, always, without a single row in a database.
Can a level be impossible?
No, and that is by construction. The grid is drawn first and the numbers are read off it, so a solution always exists. On top of that, the generator only keeps a grid that a plain line-by-line solver can finish on its own, so you never need to guess.
How does the difficulty grow?
By a table of bands, not a formula: five by five up to level 5, ten by ten to 15, twelve by twelve to 30, and fifteen by fifteen from there on. A formula that grows forever reaches an impossible level 40 that nobody ever tested. The share of filled squares stays around half on purpose: a sparser grid is not harder, it is more ambiguous, and it leaves the puzzle with more than one answer.
Where is my progress kept?
In your own browser, along with the highest level you have solved. The level itself is in the address after the hash, so you can send someone a link straight to the level you are on.