let num = 1000;

let vx = new Array(num);

let vy = new Array(num);

let x = new Array(num);

let y = new Array(num);

let ax = new Array(num);

let ay = new Array(num);

​

let magnetism = 10.0; //Strength of attraction If you make it negative, it becomes a repulsive force.

let radius = 1 ; //Radius of the circle to draw

let gensoku = 0.95; // Slow down particle movement

​

function setup(){

  createCanvas(windowWidth,windowHeight);

  noStroke();

  fill(0);

  ellipseMode(RADIUS);

  background(0);

  blendMode(ADD);

​

  for(var i =0; i< num; i++){

    x[i] = random(width);

    y[i] = random(height);

    vx[i] = 0;

    vy[i] = 0;

    ax[i] = 0;

    ay[i] = 0;

  }

}

​

​

function draw(){

  fill(0,0,0);

  rect(0,0,width,height);

​

  for(let i=0; i<num; i++){

    let distance = dist(mouseX, mouseY, x[i], y[i]); //dist(x1,y1,x2,y2) Function to find the distance between two points

    //Acceleration is inversely proportional to the square of the distance from the center of attraction.

    if(distance > 3){ //Does not update the acceleration if it is too close to the mouse

      ax[i] = magnetism * (mouseX - x[i]) / (distance * distance);

      ay[i] = magnetism * (mouseY - y[i]) / (distance * distance);

    }

    vx[i] += ax[i]; // Increase the speed vx by ax per frame.

    vy[i] += ay[i]; // Increase speed vy by ay per frame.

​

    vx[i] = vx[i]*gensoku;

    vy[i] = vy[i]*gensoku;

​

    x[i] += vx[i];  // Advance vx pixels per frame.

    y[i] += vy[i];  // Advance vy pixels per frame.

​

    let sokudo = dist(0,0,vx[i],vy[i]); // Find velocity from X and Y components of velocity

    let r = map(sokudo, 0, 5, 0, 255); //Calculate color according to speed

    let g = map(sokudo, 0,5, 64, 255);

    let b = map(sokudo, 0,5, 128, 255);

    fill(r, g, b, 32);

    ellipse(x[i],y[i],radius,radius);

  }

​

}