Chalkveil

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, without ever assuming anything. 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.

• At the end of each puzzle, the picture you filled in chalk turns into the original illustration, in high definition and in the right proportions. They are all kept in the gallery.

• Check tells you how many filled squares are outside the picture, and never which ones. An early mistake no longer costs you half an hour.

• Left in the middle of a puzzle? The grid is kept, and the menu offers to pick up where you stopped.

• 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, so 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.

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 game only talks to Google Play: to check and make purchases and, just once, to ask for a review.

Single player.