In this Blender Game Engine Tutorial #4 I cover:

-How to create multiple screens for your game (eg: menus, game-over screens)
-How to ‘program’ collision detection (switch to the ‘lose’ screen when your character touches the bad guy)
-Two types of collision detection: Material /or/ Property
-A brief introduction to properties and the Integer property type.

Where to get Blender:

Visit this Blender Game Engine Basics Series playlist: