The goal is to clear the board as fast as possible. You have to tap matches of 3 or 4 blocks to be able to slice them and make them go away. The more you get at once the more time you have added to the clock. Some blocks clear away a whole line, which is great, but be careful because they don't add any time. They should be used wisely, and with caution.
While clearing the board and beating the clock is great fun, the real glory comes with climbing to the top of the Swarm leaderboards. This competitive element really sends the game over the top. So whether you need to kill time or hone your ninja skills for other reasons, the Bushido Blocks Android game can serve you well.