Chalkveil: nonogram

The two complaints every mobile nonogram gets are always the same: ads in the middle of your reasoning and puzzles that require guessing. Chalkveil exists to have neither.

No puzzle here requires guessing. That is not a marketing promise: before it goes into the game, each of the 500 puzzles is run through a program that tries to solve it using forced deductions only — never assuming. If the grid does not close that way, the puzzle is thrown out. Because every cell was forced, it is proven at once that the solution is unique and that you can reach it by reasoning.

No ads. None, anywhere.

• 500 puzzles in five themed packs — creatures, nature, adventure, symbols and food — on 15x15, 18x18 and 20x20 grids, with difficulty climbing from two to fifteen deduction steps.

• 100 puzzles free, the whole pack. Not a sample of ten.

• No clock, no lives and no punishment in the main mode. A mistake is between you and you, and it costs nothing.

• Drag to sweep a whole line. The action is decided on the first touch and frozen until you let go — your finger never erases what it has just filled.

• Hints are free and have never been for sale. Each puzzle gives you a few, and restarting gives them all back. A hint is not currency here.

• Solving with no hints at all leaves a mark on the puzzle. It is the second layer of goal in a game where the picture, once seen, is not seen again.

Two modes for when you want pressure:

• Daily challenge — one puzzle a day, the same one for everybody, with a clock and a day streak. It may come from a pack you have not bought.

• Time trial — five puzzles in a row, times added up, no hints at all.

Six languages. A one-time purchase when you want more puzzles: no subscription, no energy, no in-game currency.

Plays offline. The network is only used if you open the store to buy, and Google Play handles the payment.

Single player. Plays with no internet.