Add symmetry docs

Author: dacap

drawing.md

@@ -31,6 +31,7 @@ Some helpers for the drawing process:
 
 * [Preview Window](preview-window.md)
 * [Tiled Mode](tiled-mode.md)
+* [Symmetry](symmetry.md)
 
 ---
 

symmetry.md

@@ -0,0 +1,34 @@
+# Symmetry
+
+To paint symmetrical sprites, you can use the Symmetry options available
+from from *View > Symmetry Options* menu. This will show you
+the following buttons in the [context bar](context-bar.md):
+
+![Symmetry Options](symmetry/symmetry-buttons.png)
+
+* ![Horizontal Symmetry Icon](symmetry/horizontal-icon.png) Enables
+  the Horizontal Symmetry
+* ![Vertical Symmetry Icon](symmetry/vertical-icon.png) Enables the
+  Vertical Symmetry
+* ![Symmetry Options Icon](symmetry/options-icon.png) Shows a popup
+  menu with a *Reset Symmetry to Center* option
+
+When you enable one symmetry axis (e.g. horizontal symmetry/vertical
+axis) you can drag-and-drop on-screen handles to configure the
+position of the axis:
+
+![Drag symmetry handles](symmetry/drag-handles.gif)
+
+Then just drawing will paint in both sides of the image:
+
+![Draw with symmetry](symmetry/draw-with-symmetry.gif)
+
+You can put the axis in the middle of a pixel if you need to:
+
+![Symmetry in the middle of a pixel](symmetry/mid-pixel.gif)
+
+---
+
+**SEE ALSO**
+
+[Drawing](drawing.md)