Kodu is a free game programming environment from Microsoft.  Formerly only for the XBox, it’s now been ported to the PC. Kodu is a visual programming language made specifically for creating games. It is designed to be accessible for children and enjoyable for anyone.

Key Features

Kodu provides an end-to-end creative environment for designing, building, and playing your own new games.

• High-level language incorporates real-world primitives: collision, color, vision
• Runs on Xbox 360 and PC
• Interactive terrain editor
• Bridge and path builder
• Terrain editor – create worlds of arbitrary shape and size
• 20 different characters with different abilities

You’ll find the following tutorial excellent in terms of getting started.