/**
 * Collision detection
 *
 * Math for artists who now need to program
 * ITP DriveBy, 10/2/2008
 * Elie Zananiri - ez@silentlycrashing.net
 */
 
//----------------------------
// variables
int staticX;
int staticY;
int staticSize;
int mobileSize;

//---------------------------- 
void setup() {
  // set up the applet
  size(300, 300);
  smooth();
  frameRate(30);
  noCursor();
  noStroke();
  
  // set the ball params
  staticSize = (int)random(10, 100);
  mobileSize = (int)random(10, 100);
  staticX = (int)random(staticSize, width - staticSize);
  staticY = (int)random(staticSize, height - staticSize);
}

//----------------------------
void draw() {
  // clear the screen
  if (areColliding()) {
    // some shade of red
    background(color(random(200, 255), 0, 0)); 
  } else {
    background(0);
  }
  
  // draw the static ball
  fill(#505EEA);
  ellipse(staticX, staticY, staticSize, staticSize);
  
  // draw the moving ball
  fill(#7BD14A);
  ellipse(mouseX, mouseY, mobileSize, mobileSize);
}

//----------------------------
boolean areColliding() {
  float currDistance = sqrt(pow(staticX - mouseX, 2) + pow(staticY - mouseY, 2));
  // alternatively, use the built-in dist(...) function
  //float currDistance = dist(staticX, staticY, mouseX, mouseY);
  float minDistance = staticSize/2 + mobileSize/2;
  
  if (currDistance < minDistance) {
    return true;
  }
  return false;
}