First 2D Game - Link directly to Creeps source code

Changes a hyperlink In the tutorial for Your First 2D game, Dodge the Creeps, to link directly to the Dodge the Creeps folder of the Godot demo projects page instead of the main repository page that contains multiple games.

getting_started/first_2d_game/index.rst

@@ -40,7 +40,7 @@ before tackling 3D games, which tend to be more complicated.
 
 You can find a completed version of this project at this location:
 
-- https://github.com/godotengine/godot-demo-projects
+- https://github.com/godotengine/godot-demo-projects/tree/master/2d/dodge_the_creeps
 
 Prerequisites
 -------------
@@ -49,8 +49,8 @@ This step-by-step tutorial is intended for beginners who followed the complete
 :ref:`Getting Started <toc-learn-step_by_step>`.
 
 If you're an experienced programmer, you can find the complete demo's source
-code here: `Godot demo projects
-<https://github.com/godotengine/godot-demo-projects>`__.
+code here: `Dodge the Creeps source code
+<https://github.com/godotengine/godot-demo-projects/tree/master/2d/dodge_the_creeps>`__.
 
 We prepared some game assets you'll need to download so we can jump straight to
 the code.