Nonogram

Nonogram is a logic puzzle game, also known as Picross or Griddlers. Every row and column of the grid has numbers beside it, and you use them to work out which squares to fill. A clue of 3 1, for example, means a block of three filled squares, then a gap, then one more filled square.

You can work through numbered levels, which start at 5 by 5 and grow to 12 by 12, or start a random puzzle at one of five difficulties, from Easy to Expert. A timer and move counter run as you play, you can undo your moves, and a hint button highlights a square you got wrong or one that still needs filling. Use the Fill and Cross buttons to mark squares, or switch on long press to cross, or a mode where each tap cycles a square through its states. Your progress through the levels is saved on the phone. Multiplayer is a shared room code: you each type the same code on your own phone and get the same puzzle to solve. The phones are not connected to each other.

The puzzles are generated by the app, and each is checked to have only one answer, so you can solve it by logic without guessing. They are random patterns rather than hand-drawn pictures. The game is free, has no ads or in-app purchases, needs no internet access and asks for no permissions.