function cross(p1,p2,p3,p4) {

  let t = (p1.x-p3.x)*(p3.y-p4.y)-(p1.y-p3.y)*(p3.x-p4.x);

  t = t/((p1.x-p2.x)*(p3.y-p4.y)-(p1.y-p2.y)*(p3.x-p4.x));

  let u = -(p1.x-p2.x)*(p1.y-p3.y)+(p1.y-p2.y)*(p1.x-p3.x);

  u = u/((p1.x-p2.x)*(p3.y-p4.y)-(p1.y-p2.y)*(p3.x-p4.x));

  return(0<u && u<1 && 0<t && t<1);

}

​

​

​

class Shape {

  constructor(n) {

    this.npoints = n;

    this.points = [];

    this.createShape(n);   

  }

  createShape(n){

    //Simple random shape generation

    //Choose n angles a and n distances r add a point at distance r from the center in direction a.

    let angles = [];

    //Random angles

    for (let i=0;i<n;i++) {

      angles.push(random(TWO_PI));

    }

    angles.sort();

    for (let i=0;i<n;i++) {

      //Change range of r for different types of shapes

      let r = random(width/8,width/3);

      this.points.push(new Point(width/2+r*cos(angles[i]),height/2+r*sin(angles[i])));

    }

  }

  contains(p) {

    //Draw a horizontal line from p. p inside the shape if odd number of intersections with the sides of the shape.

    let p2 = new Point(p.x+width,p.y);

    let count = 0;

    for (let i=0;i<this.npoints;i++) {

      if (cross(p,p2,this.points[i],this.points[(i+1)%this.npoints])) {

        count = count+1;

      }

    }

    return (count%2==1);

  }

  inside(r) {

    //Check if shape completely inside a rectangle

    //Since a rectangle is a convex shape, checking the vertices is enough

    let x;

    let y;

    for (let i=0;i<this.npoints;i++) {

      x = this.points[i].x;

      y = this.points[i].y;

      if (x<r.x || x>r.x+r.w || y<r.y || y>r.y+r.h) {

        return(false);

      }

    }

    return(true);

  }

  intersects(r) {

    //True if r inside shape or r intersects shape

    if (r.inside(this)||this.inside(r)) {

      return(true);

    }

    let r1 = new Point(r.x,r.y);

    let r2 = new Point(r.x+r.w,r.y);

    let r3 = new Point(r.x,r.y+r.h);

    let r4 = new Point(r.x+r.w,r.y+r.h);

    for (let i=0;i<this.npoints;i++) {

      if (cross(r1,r2,this.points[i],this.points[(i+1)%this.npoints])||

          cross(r2,r3,this.points[i],this.points[(i+1)%this.npoints])||

          cross(r3,r4,this.points[i],this.points[(i+1)%this.npoints])||

          cross(r4,r1,this.points[i],this.points[(i+1)%this.npoints])) {

        return(true);

      }

    }

    return(false);

  }

​

  show() {

    stroke(255,0,0);

    strokeWeight(2);

    noFill();

    beginShape();

    for (let i=0;i<this.npoints;i++){

      vertex(this.points[i].x,this.points[i].y);

    }

    endShape(CLOSE);

  }

}