public class Line{
  //member
  float x, y, xEnd, yEnd;
  int alpha;
  int steps;
  float[] scl;
  //constructor
  Line(float x, float y, float xEnd, float yEnd){
    this.x = x;
    this.y = y;
    this.xEnd = xEnd;
    this.yEnd = yEnd;
    alpha = 255;
    steps = 20;
    scl = new float[steps];
    scl[0] = 0;
    for(int i=0; i < steps; i++){
      float pre = 100000/(i+1);
      scl[i] = pre/100000;    
//      println(i+" = "+scl[i]);
    }
  }
  //method
  void setAlpha(int alpha){
    this.alpha = alpha;
    bdraw();
  }
  
  void bdraw(){
    stroke(0, alpha);
    if(steps > 0){
      pushMatrix();
      translate(x, y);
      scale(scl[steps-1]);
      line(0, 0, xEnd - x, yEnd - y);
      popMatrix();
      steps--;
    }
    else 
    line(x, y, xEnd, yEnd);
    
  }
  
  void disappear(){
    x = y = xEnd = yEnd = 1000;
    bdraw();
  }
}