Imagine a circle of radius 'power' centered on a grid at the (0, 0) location. Now draw a line from the centerpoint to any point on the circle. The length of the line, of course, is 'power'. The horizontal offset from the centerpoint the to the point on the circle is 'xSpeed' and the vertical offset is 'ySpeed'. The 'angle' is determined by the line you drew as compared to the line from the centerpoint to the point on the circle directly to the right of it (going horizontally).