An example of the second reason is serving very short left, which makes it difficult to run quick plays in the middle. Angle is a new element of the serve. Serve reception will be more difficult now that the server can serve from anywhere behind the end line. Most indoor players are not prepared to pass a hard serve down their right sideline. Generally, the lower the height, the harder it is to pass the serve.
Power is the speed of the serve.
Floaters and side-spin serves can be deceptive because the ball does not follow a straight path. Distance can be manipulated using all of the other factors, plus the server can merely step further back in the serving area. A nice hard floater can drop very quickly when served twenty feet behind the end line. Power and location are inversely related. That is, the harder you serve, the more difficult it becomes to serve to a particular location.