A free puzzle game that strengthens your mind and trains it is called Minesweeper. It's a logic puzzle that's entertaining and difficult. The objective of Minesweeper is to locate and mark all of the mines buried beneath the grey squares as quickly as you can.
How to play
Minesweeper is governed by easy rules. Mines are dispersed randomly across the board, which is divided into cells. In order to succeed, every cell must be unlocked. The number in a cell indicates the number of mines nearby. With this information, you can tell which cells have mines and which ones don't. By pressing the right mouse button, you can mark cells that you believe may contain mines.