If you like puzzles built around the idea of triggering a chain reaction check out Fractal. Played on a hexagonal board, the idea is to push selected pieces so they stimulate the others touching it to duplicate. The more pieces touching, the more new pieces you'll create. If you can create a grouping of seven pieces (six, circling the seventh) called a "bloom", it will give a massive push and hopefully in turn create more blooms, etc. Although intended as a game to purchase and download to your computer, the demo version that's up is more than enough to help you pass some time if needed.