I wonder if you could help me picking a framework/engine to use for Ludum Dare.

I previously used Scratch and Stencyl (drag&drop coding) for 2D games and now am looking for a slightly more advanced, but still quick framework. I have experience in a language similar to C++, too (Cubescript and derivates).

It should fit as many of this points as possible:
– easy to learn for someone who has medium coding experience
– flexible
– good performance
– good for creating quick prototypes
– cross platform (at least Linux and Windows)

If you have any framework in mind fitting this points, than post it in the comments below.
Thank you in advance