Official documentation of Casual Game Engine
Casual Game Engine is a 2D singleplayer top down-shooter engine which lets you create such kind of games using AngelScript as scripting language. AngelScript is an easy-to-use scripting language that has a wide popularity in the game development universe.
This documentation helps you with creating your own games using the engine.
If you need help using the engine, feel free to create a topic at the Steam discussions.
If you need help with the basics of AngelScript, have a look at the AngelScript documentation.