MineSweeper

A game we all know already since the good old days of Windows 3x. You see a board filled with mines and you don't know what fields exactly they occupy. By clicking on a field a number appears on it, which indicated how many mines are located on the nearest fields to it. Then you try and click on those fields you consider free of mines. If you make a mistake, the mine will explode and the game is over. Sometimes, especially in the beginning of the game, you just need to guess, and there's a good chance of "stepping" on a mine already in the earliest phase of the game. However, most of the time you'll need to think strategically.