Simon Tatham's Puzzles – 2015-09-10-2219-eda5a86

Collection of 38 single-player open-source logic puzzle games, free, no ads, playable offline. All generated on demand with adjustable size/difficulty, so you'll never run out of puzzles. Various control options for small screens: on-screen arrow keys pinch to zoom, and a new button to swap press/long-press.