For Comp446, Programming Methodologies with C++ (something like that), we had to do a program. So me and my team mate, did a Space Shooter Engine. With plans of making it into a MMORPG in the future.

These few screenshots partially show the capabilities of that engine.
The scene has been put together through a scripting system that the engine understands.





It was nothing hard to do, but useful at the end.
All that would be left to do, is create a level editor that can write script language. Then users can create levels (or entire games) simply point and click.