Originally Posted by

**Jonax**
The reason for this to simplify the programming of course. I'm afraid letting the ball cross that line may cause a host of new programming headaches. If I had tried that apporoach I'd probably still be sweating over special cases and have nothing to show. On the other hand it may not be so bad and improved gameplay is priceless.

If you start using relative distance from the center of the ball against center of the playfield I believe you could perhaps even simplify your programming quite a bit.

First you need to make sure that your playfield coordinates are position so that the position 0:0 will be in the center of your playfield. I'm guessing you are now working with Window coordinates. So you would make this transformation by simply subtracting half of the width of your playfield window width from X coordinate and half of your playfield window height from Y coordinate.

For instance in my quick mock up I use mouse for moving the ball so I transform my mouse coordinates to PlayfIeld coordinates using

Code:

PlayfieldX := X-(PaintBox1.ClientWidth div 2);
PlayfieldY := Y-(PaintBox1.ClientHeight div 2);

I then pass this Playfield coordinates to my Collision detection procedure that looks like this

Code:

procedure TForm5.CheckCollision(X,Y: Integer);begin
//Reset collisions
TopBorderCollision := False;
BottomBorderCollision := False;
LeftBorderCollision := False;
RightBorderCollision := False;
//Check for top/bottom collisions
if Abs(Y) > ((PaintBox1.ClientHeight div 2)-BorderThickenss) then
begin
if Y < 0 then
begin
TopBorderCollision := True;
end
else BottomBorderCollision := True;
end;
//Check for left/right border collisions
if Abs(X) > ((PaintBox1.ClientWidth div 2)-BorderThickenss) then
begin
if X < 0 then
begin
LeftBorderCollision := True;
end
else RightBorderCollision := True;
end;
//Check to see if ball is in slowdown area then reduce its speed
if ABS(X) > ((PaintBox1.ClientWidth div 2)-BorderThickenss-SlowdownAreaWidth) then BallSpeed := 20
//else keep it moving at full speed
else BallSpeed := 20;
//Check paddle collision
if X > 0 then
//Player padle collision
begin
//Simple collision checling against paddle using X coordinate of the ball
//Ball Y position si within player paddle area
if (Y >= PlayerPaddle.Top) and (Y <= (PlayerPaddle.Bottom)) then
begin
if ABS(X) > ((PaintBox1.ClientWidth div 2)-PlayerPaddle.Width) then //Bounce the ball from the paddle by multiplying X speed by -1;
end
//Because the ball Y position is not within the PlayerPaddle area it means we will have to check collision
//against PlayePaddle corners instead
else
begin
//Top corner
if System.Math.Hypot(ABS(X-PlayerPaddle.Right),ABS(Y-PlayerPaddle.Top)) < BallDiameter then
begin
//Bounce ball from top paddle corner. It would probably result in great change of the ball trajectory angle
end;
//Bottom corner
if System.Math.Hypot(ABS(X-PlayerPaddle.Right),ABS(Y-PlayerPaddle.Bottom)) < BallDiameter then
begin
//Bounce ball from top paddle corner. It would probably result in great change of the ball trajectory angle
end;
end;
end;
end;

I hope my code mock up can give you good enough idea of how to work with such approach and how easy it actually is. I tried to comment it as good as I can so ti can be even more understandable.

I'm guessing you will have to make some changes so that it will work with your data structures

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