Slide Puzzle is a jigsaw-style challenge with a calm feel. A picture is cut into square tiles with one space left empty. Tap a tile next to the empty space to slide it over, and keep sliding until the whole image is reassembled in order. You can choose an easier grid when you are starting out and a larger one as you grow confident.
This puzzle is a fine workout for spatial reasoning and planning. To solve it you picture the finished picture, decide which tile must move next, and look a few steps ahead, all of which keep the visual and problem-solving parts of your mind active. The unhurried pace makes it a soothing break in the day. It is free to play in your browser with no download, and the tiles are large enough to tap comfortably, so it is easy on the eyes and the hands.