Hi,
Raydium is definitely a 3D engine. There's no easy way to create real 2D things with it. However, it's quite easy to make things *looks* like 2D, so you won't have to create a whole 3D "world". For instance, if you lock your camera above the pool table, there's no need for modeling the bottom of the table. And you can still allow you camera to move a bit, in a sort of 2.5D, in this example.
But your world will be (at least a bit) 3D, as your physics. The good news is that for this type of games, it's almost as easy in 3D than 2D, to my opinion. A pool ball is not exactly "hard" to shape in 3D, for instance
To answer your questions:
- You need to know C (or C++, whatever, the engine is pure C) and ... Raydium itself. The rest will come as you discover the engine (I'm thinking about all the 3D vocabulary: texture, vertex, etc).
- The wiki and, probably more importantly, the demos provided with the engine are the best way to understand how it works. Just modify, tweak and hack them. And then, there's this forum where we try to answer at every question.
Good luck for this project ! (and have fun
)