Minesweeper meets Sudoku meets hexagons. HexCells Infinite (and the two previous games, HexCells and HexCells Plus) is a great puzzle game with lots of replayability. It's perfect for relaxing while listening to something else.

I'd recommend playing HexCells and HexCells Plus first just because they ease you into the game a bit more smoothly, but if you're only going to get one, HexCells Infinite is by far the best due to the added feature of randomly generated levels.

Fantasic little puzzle game, took me about 2.5 hours to complete. It's basically Minesweeper meets Sodoku meets hexagons.