Hi,

I'm looking for 2D games (preferably small and open-source) in order to analyze and understand some aspects from game engine design such as event handling, entities models, 2D vector using, physics, etc. I don't care the language.

Thanks.

You could perhaps try Secret Maryo Chronicles, Battle for Wesnoth or Hero of Allacrost, but I'll just quickly quote some advice I gave in another recent topic:

I do have some advice on learning from sourcecode however: remember that you're seeing an end product rather than the process that went along with it. When you're looking at sourcecode you can (usually) figure out the how but not the why. You don't know if the programmer used a particular technique because they thought it was best, because they were simply unaware of alternatives, because they had to meet specific requirements that you might have, etc. I never go so far as to tell someone they shouldn't bother reading source-code from completed games, but be sure you take what you see with a healthy grain of salt. Just because it worked for them doesn't necessarily make it a good choice for you.

...and speaking of that other recent topic, you'll find a couple of other links suggested in there.