Although I can't give you exact specs yet, I can tell you that the game won't require a whole lot of power to run. If you're used to playing modern games on your PC, then you'll be just fine.
To give you a bit of perspective, the first three months of development took place exclusively on my laptop, which has a Core 2 Duo processor and GeForce 9400m graphics chip. In other words, a laptop with just about zero gaming capability. Even with these specs, I was able to run smoothly at medium quality.
The LT Engine is quite efficient, but it also doesn't leverage any extremely expensive graphical techniques, so you shouldn't have to worry much about your specs!
Not likely. If we exceed our goal by a significant amount, it's possible that I will announce multiplayer support as a far-off stretch goal, but I don't anticipate reaching it. I need to make sure that I can complete LT in a reasonable amount of time...and, realistically, adding multiplayer would increase the development time by a significant amount!
Don't see the answer to your question? Ask the project creator directly.