I've worked what was wrong. I thought that a vector pointing straight up ( x = 0 y = -0) would be an angle of zero, so you'd get the same value, but an angle of 0 in atan2 is x = 1 y = 0. So I was  changing the wrong component in newSpeed. Anyway I have other problems, I'm trying to make my own Vector2.Reflect method but its ...

Right now I am using matrices to rotate vectors, but they seem to not be working as I would understand them to. Here is some code.                         Matrix transform = Matrix.CreateRotationZ((float)Math.Atan2(endToBall.Y, ...

"Whats wrong with the dot product solution that was suggested earlier?" I don't get it.

Okay, its basically circle collision and reflection, except one circle doesn't move. Forget the infinitely small object thing, all a radius of zero does is make the collision system not take into account the radius of the other circle, for example: // if circle a is the ball and circle b is the point. if((circleB - circleA).Length < ...

Let me clarify, I am basically trying to bounce a circle, off of another circle where the second circle doesn't move at all and has a radius of 0.

I am just about to smash my keyboard into the wall with this one. Basically I am making a 2D game where you play as a ball with lots of lines around you that you can bounce off. So far, you can bounce off the lines if you hit them completely on one of the flat sides. To do this it uses a matrix representing the transformation of the line (lines ...

Basically I want to make this FPS style game, and all the experience I have with XNA is 3D pong + some very basic knowledge of vector math. Basically I need to somehow learn how to do ray collision with 0 tutorials of how to do it on the internet. I need to use an algorithm where you put in a starting position and an angle that gives you the ...

Meh, I guess that I'll have to forget about XNA. Too many requirements for me to make crappy games to run on school computers.

Is it possible to compile a game into a single .exe file? I don't just mean the content, I mean the whole thing, so the game can work without XNA FrameWorkz installed. Right now I would be happy with getting just the framework into the .exe. The content isn't that much of an issue.

Yea, that was the problem. I remember reading that on wikipedia. That / 2 thing was because I copied it from my last code for drawing lines, where a line has two verts in it. So four lines would be 8 verts.