I'm looking into making a little "grand strategy" game in the line of Europa Universalis or Crusader Kings by Paradox Development Studio, as a free time project for personal learning and amusement. It'd be focused on singleplayer (but I'd like to be able to implement multiplayer later on if I'm succesful).
For those who don't know these games, the main interface is a world map divided in provinces owned by entities (nations or characters depending of the game). Both characters/nations and provinces have a wide range of different stats and attributes. A player can select to control one nation/characters, and the AI controls all others.
As it'll be my first project, I want it to be wholly 2D. Also, since there is going to be a lot of calculations running constantly, I'd like to be able to get the most efficiency in the programming language as possible.
On the other hand, I want the game to be very moddable, with the end user being able to use a custom scripting language to manipulate the ui and the game mechanics.
Since I'm new to game development, I'd like to find a platform with a not too steep learning curve.
Lastly, as the title implies, I'd like it to be free.
I'm not sure if there any developing platform that fullfills this criteria, but if it isn't, which would fullfil most of them?