[css-round-display] Update the polar coordinate system's general description

Author: hyojinLGE

css-round-display/Overview.bs

@@ -11,7 +11,6 @@ Editor: Soonbo Han, LG Electronics, soonbo.han@lge.com
 Abstract: This document describes CSS extensions to support a round display. It extends existing CSS features including Media Queries[[MEDIAQUERIES-4]], CSS Shapes[[CSS-SHAPES-1]], Borders[[CSS3-BORDER]], and Positioned Layout[[CSS3-POSITIONING]]. The extensions will help web authors to build a web page suitable for a round display.
 </pre>
 
-
 <h2 id="introduction">Introduction</h2>
 <p>
 Everything on the web is a rectangle. For example, the window content area in a web browser is a rectangle. Each HTML element follows the W3C box model and thus is also a rectangle. New devices with a round display are now emerging. The current web standards lack some features to support the devices as follows:
@@ -271,8 +270,12 @@ The example below shows how the 'border-boundary' property works on drawing bord
 </p>
 
 <h2 id="positioning-content">Positioning content by using the polar coordinate system</h2>
+
 <p>
-Elements are often placed along a circle or concentric circles, and polar coordinates are useful to handle such cases. This section introduces polar positioning to support layout of elements in the polar coordinate system where the position of an element is determined by a distance from a fixed point within the containing element and an angle from a fixed direction. We add '<code>polar</code>' to the value of the 'position' property to support the polar coordinates of the children of an element. The 'polar-angle' and 'polar-distance' properties specify the position of an element (or a child).
+Elements could be often placed along a circle or concentric circles, and the polar coordinate system is useful to handle such cases. This section introduces polar positioning to support layout of elements in the polar coordinate system where the position of an element is determined by a distance from a fixed point within the containing element and an angle from a fixed direction. We add '<code>polar</code>' to the value of the 'position' property to support the polar coordinates of the children of an element. The 'polar-angle' and 'polar-distance' properties specify the position of an element (or a child).
+</p>
+<p class="note">
+In the polar coordinate system, a point is described as being a certain distance (r) from the pole and at a certain angle (theta) from the polar axis. In the mathematical theory, the polar axis is commonly defined as the positive direction of the x-axis, but we consider the polar axis as the positive direction of the y-axis position as other CSS specifications usually do.
 </p>
 <h3 id="position-property">The 'position' property</h3>
 When the 'position' property on an element is set to '<code>polar</code>', its children use the polar coordinates.