let oldX, oldY;

let draw_line;

const G = 0.0000001;

let id = 0;

let to_delete = -1, delete_index;

​

function setup() {

  frameRate(60);

  createCanvas(400, 400);

  planets.push(new Planet(width/2, height/2, 0, 0, 50, id));

  id += 1;

  /*planets.push(new Planet(width/4, height/2 - 1, 0, 1, 5, id));

  id += 1;*/

}

​

function draw() {

  background(220);

  if (draw_line) {

    dashed_line(oldX, oldY, mouseX, mouseY);

  }

​

  for (planet of planets) {

    planet.draw();

    planet.update_posit();

    planet.collision_detect();

  }

  if (to_delete != -1) {

    delete_index = 0

    for (planet of planets) {

      if (planet.id == to_delete) {

        break;

      }

      delete_index += 1;

    }

    planets.splice(delete_index, 1);

    to_delete = -1;

  }

  for (planet of planets) {

  planet.update_accel();

  }

}

​

function mousePressed() {

  oldX = mouseX;

  oldY = mouseY;

  draw_line = true;

}

​

function mouseReleased() {

  let vx = ( oldX - mouseX) / 50;

  let vy = ( oldY - mouseY) / 50;

  planets.push(new Planet(oldX, oldY, vx, vy, 5 + random(), id));

  id += 1;

  draw_line = false;

}

​

function dashed_line(x1, y1, x2, y2) {

  let distance = Math.sqrt((x2-x1)**2 + (y2-y1)**2);

  let num_lines = distance / 20;

  let xfrac = (x2-x1)/num_lines;

  let yfrac = (y2-y1)/num_lines;

  for (let i = 0; i < num_lines; i+= 2) {

    line(x1 + xfrac*i, y1 + yfrac*i,

        x1 + xfrac*(i+1), y1 + yfrac*(i+1));

  }

}

​

class Planet {

  constructor(initX, initY, initVX, initVY, diameter, id) {

    this.position = createVector(initX, initY);

    this.velocity = createVector(initVX, initVY);

    this.diameter = diameter;

    this.mass = diameter**3;

    this.id = id;

  }

  draw() {

    ellipse(this.position.x, this.position.y, this.diameter);

  }  

  update_accel() {

    let accel = createVector(0,0);

    let r, r_unit, single_accel;

    let plan1, plan2;

    for (planet of planets) {

      if (this.id == planet.id) {

        continue;

      }

      plan1 = planet.position;

      plan2 = this.position;

      r = p5.Vector.sub(plan1, plan2);

      r_unit = r.normalize();

      single_accel = (G * planet.mass) / (r.magSq());

      accel.add(r_unit.mult(single_accel)); 

    }

    this.velocity.add(accel);

  }

  update_posit() {

    this.position = this.position.add(this.velocity);

  }

  collision_detect() {

    let dist_vec, dist_scal;

    for (planet of planets) {

      if (this.id == planet.id) {

        continue

      }

      dist_vec = p5.Vector.sub(this.position, planet.position);

      dist_scal = dist_vec.magSq();

      if (dist_scal < (this.diameter/2 + planet.diameter/2)**2) {

        /*console.log("Collision between " + this.id + " of mass " + this.mass + " and " planet.id + " of mass " + planet.mass);*/

        console.log(this.id, this.mass, planet.id, planet.mass);

        if (this.mass > planet.mass) {

          to_delete = planet.id;

        }

        else if (this.mass < planet.mass) {

          to_delete = this.id;

        }

        else {

          to_delete = planet.id;

        }

        console.log("Delete ID " + to_delete);

      }

    }

  }

}