Make experimental API not hidden in the docs anymore

docs/reST/index.rst

@@ -38,6 +38,41 @@ section below, check out a video tutorial (`I'm a fan of this one
 <https://www.youtube.com/watch?v=AY9MnQ4x3zk>`_), or reference the API
 documentation by module.
 
+Experimental modules
+--------------------
+
+Experimental modules are work in progress, this is why you should refrain from relying on any features 
+provided by these modules, as they are subject to change or removal without prior notice. 
+If you want to test these experimental modules, you might want to understand how you import 
+them, this is how you can do it:
+
+.. code-block:: python
+
+  from pygame import experimental_module
+  # Or for specific modules like _sdl2.controller
+  from pygame._sdl2 import controller
+  # Or
+  import pygame.experimental_module
+
+Don't forget to report us any problem with the experimental features on `github`_ so we can easily 
+turn them to stable API in the future ^^.
+
+**Below is currently the list of experimental modules :**
+
+:doc:`ref/geometry`
+  Pygame module for the Circle, Line, and Polygon objects.
+
+:doc:`ref/window`
+  Pygame object that handles a window.
+
+:doc:`ref/sdl2_controller`
+  Pygame module to work with controllers.
+
+:doc:`ref/sdl2_video`
+  Pygame module for porting new SDL video systems.
+
+.. _github: https://github.com/pygame-community/pygame-ce
+
 Documents
 ---------
 

docs/reST/themes/classic/elements.html

@@ -39,8 +39,9 @@ <h5>pygame-ce documentation</h5>
 
 #}
 {%- set basic = ['Color', 'display', 'draw', 'event', 'font', 'image', 'key', 'locals', 'mixer', 'mouse', 'music', 'pygame', 'Rect', 'Surface', 'time'] %}
+{%- set experimental = ['sdl2_video', 'controller', 'geometry', 'Window'] %}
 {%- set advanced = ['BufferProxy', 'freetype', 'gfxdraw', 'midi', 'PixelArray', 'pixelcopy', 'sndarray', 'surfarray', 'cursors', 'joystick', 'mask', 'math', 'sprite', 'transform'] %}
-{%- set hidden = ['sdl2_video', 'sdl2_controller', 'geometry', 'Window'] %}
+{%- set hidden = ['sdl2_video', 'geometry', 'Window'] %}
 {%-   if pyg_sections %}
 	  <p class="bottom"><b>Most useful stuff</b>:
 {%      set sep = joiner(" | \n") %}