Spring RTS Engine

If it's a board game why not use a word processor for rules and a printer for cards? IRL game programming has a very intuitive interface.

Edit: oops, not multi-platform.

whats wrong with making a board/cards game in C# or VB.NET?

Do you have the mechanics of how the game would work from a user interface point of view? aka you could create a basic storyboard in your mind?

I would not use VB .Net, I would stick to C# as VB is well, eurgh, and the C syntax is far more valuable.

dude... why it has to be multiplatform if its just a prototype?

just get Multimedia Fusion 2 and start making your prototype ready...

you can waste more time finding that perfect multiplatform gamemaker tool, or you can start making it on windows already...

sure it costs money, but you can pretend you have that money and just use this program you google for.

What about Processing? Pretty neat, Java/flash mixup.
Example game written in it: Wayfarer