This property only applies to linear gradients.
This property defines the angle the gradient path makes with the horizontal plane.
For example, a gradient which extends from left to right can be changed to extend from bottom to top by setting this property to 90 degrees.
A value of 45 degrees yields a gradient which extends from the bottom left corner of the containing element to the top right corner.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2