PVector[] v;
PVector dv;
int bs = 5, count=1, index=-1;
boolean bover = false;
boolean locked = false;

void setup() 
{
  size(600, 600);
  v = new PVector[32];
  v[0] = new PVector(40, 20);
  dv = new PVector(0, 0);
  rectMode(RADIUS);  
}

void draw() 
{ 
  background(128);
  fill(0,153,255);
  drawPoints();
}

void drawPoints()
{
  int  i;
  for(i=0; i<count; i++) {
    if(index==i) stroke(0,255,0); 
    else stroke(255,153,0);
    rect(v[i].x, v[i].y, bs, bs);
  }
  stroke(255); 
  for(i=0; i<count-1; i++) 
    line(v[i].x, v[i].y, v[i+1].x, v[i+1].y);  
}  

void mouseMoved()
{
  int i=0;
  index = -1;
  bover = false;
  for(i=0; i<count; i++) {
    if (mouseX>v[i].x-bs && mouseX<v[i].x+bs && mouseY>v[i].y-bs && mouseY<v[i].y+bs) {
      index=i;
      bover = true;
      return;  
    } 
  }  
}  

void mousePressed() 
{
  if(bover) { 
    locked = true; 
    dv.x = mouseX-v[index].x; 
    dv.y = mouseY-v[index].y; 
  } 
  else {
    if(count<32) {
      v[count] = new PVector(mouseX, mouseY);
      count++;
      index=count;
    }
    locked = false;
  }
}

void mouseDragged() 
{
  if(locked) {
    v[index].x = mouseX-dv.x; 
    v[index].y = mouseY-dv.y; 
  }
}

void mouseReleased() 
{
  locked = false;
}