I am programming an warlords clone using openGL and c++.I have drawn the ball and the paddles and the castles,I need an algorithm for collision detection of when the ball hits the castle walls, and the paddles, I am trying to avoid alot of complex math and physics,here is my collision detection so far: //check for collision detection if (x+20.0 > i && x < i+80.0f && y < 40.0f) { ystep=-ystep; } if (x+20.0 > i && x < i+80.0f && y > 580.0f) { ystep=-ystep; } this checks to see if the ball hits the paddle

I need an algorithm for when the ball hits a castle wall

you posted this same question a few days earlier (http://www.gamedev.net/community/forums/topic.asp?topic_id=389421), there's really no need to double-post.

I'm not too familiar with the game, but as I mentioned in the earlier thread there's a pretty simply way to test for collision between a circle and a wall:

|
| (C)
|
|
|
o-->N
P

Given a circle with center C, radius R, and a wall originating at point P with a (normalized) outward (I said inward last time, which was a mistake, sorry) normal N:

vector v = C - P;
projection of v onto n = (v dotproduct N) * N;
if (magnitude(projection) <= R)
//collision occured

Hope it helps.