Hey buddies, I have the following program that I made [college homework]

*** My doubt is in the "Void Principal" part of the program! [take a look, please]
They want us to have a blue ball moved by the mouse cursor [ok, i did that]... and at the same time they want red balls coming from the TOP of the screen [ONE by ONE] going to different directions! The program will finish when we hit the blue ball in one of the red balls... that's when my doubt starts! I created a FOR command for the red ball... but this For command never stops, so, the next red ball never comes! I'd like a help of you to make the next balls come from the top of the screen... and if u also could take a look at what I did in the IF command I opened to make the program finishes when the red ball is hit by the blue one! I think it's not right at all! Please, help me!!!

Thank u so much!!!

Hey Paul, thanks for your help!
But I'm very new to allegro, so I don't understand this tags =/

Could u explain that to me, or someone else?!

Ok, I edited it

Now, could u help meeeeee?!

This is the code in question. It is called your "main loop". If you look at what's happening, it's not at all what you need to be happening.

The while part is good. You want your code to run until the escape key is pressed. In other words, while the escape key is not pressed. That's fine. Inside the loop, You need to separate your code into logic and drawing.

First, make a list of what you need to keep track of. In this case, it's the ball's position. Store these variables outside of the loop:

// ...
int ball_x, ball_y;
while(!(key[KEY_ESC]))
{
    // Logic:
    // Drawing:
}

Then, in the logic section, move the ball by changing ball_x and ball_y. Also check if the player has moved the mouse over the ball in this section. And finally, in the drawing section, draw the player's ball using mouse_x and mouse_y and draw the ball using the stored ball_x and ball_y.

I hope that all makes sense. Don't worry if the ball zooms off-screen faster than you can hover over it. You'll need to get into timers to fix that issue.

Try this:

However, this:

if ((mouse_x == i) && (mouse_y == i))
    {
      finaliza();
      exit(-1);
    }

won't work as a collision detection.

Yes of course, what did you expect? I posted that just to 'stop' your neverending for(). If you want balls in different directions you should use vectors, something like this:

double theta = angle;
x =  x_start_position + cos(theta) * distance;
y =  y_start_position + sin(theta) * distance;
distance++;

Put a bounding box in each ball, do the collision detection between both boxes using this function:

x1,y1             
   +----+
   |RED |
   |BALL|
   +----+x2,y2
xx1,yy1             
   +----+
   |BLUE|
   |BALL|
   +----+xx2,yy2

inline bool collide(int x1, int y1, int x2, int y2, int xx1, int yy1, int xx2, int yy2)
{
     if (x2 <= xx1) return false;
     else if (x1 >= xx2) return false;
     else if (y2 <= yy1) return false;
     else if (y1 >= yy2) return false;
     else return true;
}

Box collision is easier to understand than circle/cirlcle collision, that's why I showed him the b. box collision function. Also, I think he does not need so much precision in his program.
However, Miran's code is the best way to solve this problem, obviously.

No, it's me too. Even when you go into bouncing reaction, the circle-circle thing is not very difficult. You can define a line from one circle to the other (middle points), you can find out the collision point on this line, you can define the tangential line through this point. Now you have an imaginary wall that both circles collide against. And so on.

Yes.

My thought exactly.
Break the problem down into sub-problems until you reach something you can't divide any further. If you can solve it, do so. If you can't, come back here.

Here are a few things to google / forum-search:
- main loop
- collision detection
- separate logic and drawing
and more generally:
- game programming

Set up a main loop. This should do logic and drawing.
Logic needs to:
- update player position
- update ball position
- check if ball hits player -> end game
- check if ball is outside screen -> reset ball coordinates and speed
Drawing is just drawing.

...

No Tobias, I didn't ask anyone to DO my homework... I just asked for HELP!
That's different, ok?

Anyway, I wanna thank everyone who came here to gimme a help!
I made some changes and now the program's workin' perfectly!

Thank u guys...