const drag_force = 0.5;

const maxV = Math.PI/64;

​

const list = new List(5);

const canvas_size = 800;

var inscreen = false;

var origin;

​

function setup() {

  can = createCanvas(canvas_size, canvas_size);

  can.mouseOver( () => inscreen = true );

  can.mouseOut( () => inscreen = false );

​

  sl1 = createSlider(canvas_size/32, canvas_size/16, canvas_size/24, 0.25);

  sl1.parent('div1')

  sl2 = createSlider(4, 16, 8, 1);

  sl2.parent('div1')

  origin = createVector(canvas_size/2, canvas_size/2);

  colorMode(HSB)

  noCursor();

}

​

var frame = 1;

var accumulative = 0;

var radius = 0;

​

function mousePressed () {

  if(!inscreen) 

    return;

  frame = 1;

  accumulative = 0;

  radius = createVector(mouseX, mouseY).sub(origin).mag();

  if(radius < canvas_size*0.05/2 + sl1.value()) radius = 0;

}

​

function mouseDragged() {

  const last_frame = createVector(pmouseX, pmouseY).sub(origin).heading() + TWO_PI;

  const current_frame = createVector(mouseX, mouseY).sub(origin).heading() + TWO_PI;

  //console.log(accumulative/frame)

  frame++;

  if( abs(current_frame - last_frame) < TWO_PI-PI/8 )

    accumulative += current_frame - last_frame;

​

}

​

function mouseReleased() {

  ball = {

    rad: radius,

    angle: createVector(mouseX, mouseY).sub(origin).heading() + TWO_PI,

    angleV: constrain(accumulative * drag_force / frame, -maxV, maxV),

    size: sl1.value(),

    hue: random(-PI,PI),

    sat: random(-PI,PI)

  }

  if(ball.angleV == 0) ball.angleV = random(-maxV, maxV)*0.25;

  if(inscreen || radius != 0) list.add(ball);

  radius = 0;

}

​

function draw() {

  colorMode(RGB)

  background(0, 16);

  fill('#007fff');

  noStroke();

  textSize(16)

  textAlign(LEFT, CENTER)

  if(frameCount % 30 == 0) list.resize(sl2.value());

  text( list.current_size + ' / '+ sl2.value() + ' Orbits', 16, 25);

  const pvec = createVector(mouseX, mouseY).sub(origin)

  const vec = createVector(mouseX, mouseY).sub(origin);

  colorMode(HSB)

  fill(map(sin(vec.heading()), -1, 1, 0, 256), 256, 256, 4);

  //push();stroke(0);fill(0, 256);circle(pmouseX, pmouseY, sl1.value());pop();

  if(!mouseIsPressed)

    circle(mouseX, mouseY, sl1.value())

  vec.setMag(radius);

  translate(origin)

  circle(vec.x,vec.y, sl1.value())

  circle(0,0,sl1.value())

  list.iterate( (data) => {

    fill(map(sin(data.angle+data.hue), -1, 1, 0, 256), 

         map(cos(data.angle+data.sat), -1, 1, 128, 256), 256, 256);

    circle(cos(data.angle) * data.rad, sin(data.angle) * data.rad, data.size);

    data.angle = (data.angle + data.angleV) % TWO_PI;

    collision_detection(data);

  });

}

​

​

function get_pos (ball) {

  return p5.Vector.fromAngle(ball.angle).setMag(ball.rad);

}

​

function collision_detection (ball) {

  const pos = get_pos(ball);

​

  list.iterate( (ball2) => {

    if(ball.id != ball2.id && pos.dist(get_pos(ball2)) < ball2.size/2 + ball.size/2) 

      handle_collision(ball, ball2);

  })

}

​

function handle_collision(ball, ball2, pos, pos2) {

    const mass1 = ball.rad*ball.rad*PI;

    const mass2 = ball2.rad*ball2.rad*PI;

    const impulse1 = mass1 * ball.angleV;

    const impulse2 = mass2 * ball2.angleV;

    ball.angleV = impulse2 / mass1;

    ball2.angleV = impulse1 / mass2;

    ball.angleV = constrain(ball.angleV, -maxV, maxV);

    ball2.angleV = constrain(ball2.angleV, -maxV, maxV);

    ball.hue = random(-PI, PI);

    ball2.hue = random(-PI, PI);

    ball.sat = random(-PI, PI);

    ball2.sat = random(-PI, PI);

    while(get_pos(ball).dist(get_pos(ball2)) < ball2.size/2 + ball.size/2) {

     ball2.angle = (ball2.angle + ball2.angleV  ) % TWO_PI;

     ball.angle = (ball.angle + ball.angleV  ) % TWO_PI;

    }

}