# Coordinates, Points and Rectangles

The coordinate system of a Window or View has (0, 0) at the top left corner, with x coordinates increasing to the right and y coordinates increasing downward. The coordinates label infinitely thin horizontal and vertical lines, and pixels exist between these lines, as illustrated in the figure below.
A point is represented by a 2-tuple (x, y). A 2-tuple can also be used to represent as size (width, height) or a relative displacement (dx, dy).
A rectangle is represented by a 4-tuple (left, top, right, bottom). If right <= left or bottom <= top, the rectangle is an empty rectangle and is considered to enclose no pixels.
Angles are measured in degrees anticlockwise from the x-axis.
The Geometry submodule provides a collection of functions for operating on points and rectangles.
Relationship between coordinates, pixels, points and rectangles