sketch.js

let num = 1000;
let x = new Array(num);
let y = new Array(num);
let r = new Array(num);
let speedY = new Array(num);

function setup() {
  createCanvas(600, 600); //ウィンドウサイズの指定
  background(0, 0, 0); //背景色を指定して1回だけ塗る。

  for (let i = 0; i < num; i = i + 1) {
    x[i] = random(0, 600);
    y[i] = random(0, 600);
    r[i] = 50;
    speedY[i] = random(2, 20);
  }
}

function draw() {
  background(0, 0, 0); //背景色を指定して1回だけ塗る。
  for (let i = 0; i < num; i = i + 1) {
    //fill(0, 255, 0);
    stroke(100, 255, 0);
    strokeWeight(0.2);
    rect(x[i], y[i], 0.5, 20);
    y[i] = y[i] + speedY[i];

    if (y[i] > 600) {
      y[i] = 0;
    }
    if (y[i] < 0) {
      speedY[i] = speedY[i] * -1;
    }
    // if (dist(x[i], y[i], mouseX, mouseY) < r[i]) {
    //r[i] = r[i] + (200 - r[i]) / 10.0;
    //} else {
    //r[i] = r[i] + (50 - r[i]) / 10.0;
  }
}

function mousePressed() {
  //マウスのボタンが押し下げられた時の処理
}

function mouseReleased() {
  //マウスのボタンが離された時の処理
}

function keyPressed() {
  if (key == "s") {
    saveCanvas();
  }
}