Slide the ball around the grid picking up the gems. Every time the ball moves, it will keep sliding until it either hits a wall, or stops on a stop square (the broken circles). Try to collect every gem without running into any of the mines.
Use the numeric keypad to slide the ball horizontally, vertically or diagonally. Alternatively, click on the grid to make the ball move towards where you clicked.
If you hit a mine and explode, you can select Undo from the Game menu and continue playing; the game will track how many times you died.