Each bar graph is a brick, take buy a bill now as an example, the brick that is in lowest position at the moment, go to the left, when the brick with the 3rd highest is in existence, take the height of this brick as a benchmark, when the price exceeds the height of this brick, can establish buy a bill, when appear opposite circumstance closes a position, establish empty order at the same time. This is a simple rule, need each friend grope by oneself.
