noc.html

<script 
  src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.10.2/p5.min.js"></script>
<script>

  class Particle {
    constructor() {
      this.position = createVector(20, 20)
      this.radius = 15
      this.velocity = createVector(1, 1)
      this.acceleration = createVector(0.0, 0.0)
    }

    render () {
      const diameter = this.radius * 2
      ellipse(
        this.position.x, 
        this.position.y, 
        diameter
      )
    }

    update() {
      this.position.add(this.velocity)
      this.velocity.add(this.acceleration)
      this.acceleration = 
        createVector(mouseX, mouseY)
          .sub(this.position)
          .mult(0.001)
      this.velocity.limit(5)
    }
  }  

  let particle

  function setup() {
    createCanvas(400, 400)
    background('#99ccff')
    particle = new Particle()
  }

  function draw() {
    background('#99ccff')
    particle.render()
    particle.update()
  }

</script>