const boldMode = false;

const debugText = false;

const fullSize = true;

​

const charStr = '012345789Z:・."=*+-<>¦｜_/\\';

​

let symbols = [];

​

let chars = [];

let droppers = [];

let lifespan = [];

let colors = [];

​

let charWidth;

let charHeight;

​

let charSize = 16;

​

function setup() {

  if (fullSize)

    createCanvas(window.innerWidth, window.innerHeight);

  else

    createCanvas(412, 412);

  colorMode(HSL, 360, 255, 100);

  noStroke();

  textSize(charSize);

  textAlign(CENTER);

  textFont('monospace');

  if (boldMode)

    textStyle(BOLD);

  charWidth = round(width / charSize);

  charHeight = round(height / charSize + 1);

  generateSymbols();

  for (let y = 0; y < charHeight; y++) {

    for (let x = 0; x < charWidth; x++) {

      let c = randomCode();

      chars.push(c);

      lifespan.push(0);

      colors.push(0);

    }

  }

  for (let i = 0; i < charWidth * 1.5; i++) {

    droppers.push(new Dropper(

      round(random(charWidth)),

      round(random(charHeight))

    ));

  }

}

​

function draw() {

  background(0);

  translate(charSize / 2, 0);

  for (let y = 0; y < charHeight; y++) {

    let yp = y * charSize;

    for (let x = 0; x < charWidth; x++) {

      let i = x + y * charWidth;

      if (random() < 0.05)

        chars[i] = randomCode();

      let ls = lifespan[i];

      if (ls > 0) {

        lifespan[i] -= 2;

        if (lifespan[i] < 50)

          colors[i] = lifespan[i];

        fill(140, 255, colors[i]);

        text(chars[i], x * charSize, yp);

      }

    }

  }

  for (let i = 0; i < droppers.length; i++) {

    let d = droppers[i];

    let py = floor(d.y);

    d.y += d.speed;

    if (d.y > charHeight) {

      d.y = 0;

      // d.x = floor(random(charWidth));

    }

    let ry = floor(d.y);

    if (ry - py >= 1) {

      let previ = d.x + py * charWidth;

      let newi = d.x + ry * charWidth;

      lifespan[previ] = 80;

      colors[previ] = 50;

      lifespan[newi] = 100;

      colors[newi] = 100;

    }

  }

  if (debugText) {

    fill(255);

    text(frameRate(), 12, 12);

  }

}

​

function Dropper(x, y) {

  this.x = x;

  this.y = y;

  this.speed = 0.5;

  this.lifespan = 100;

}

​

function generateSymbols() {

  for (let i = 0; i < 96; i++)

    symbols.push(String.fromCharCode(0x30A0 + i));

  // for (let i = 0; i < 10; i++)

  //   symbols.push(i);

  symbols.push(...charStr.split(''));

}

​

function randomCode() {

  // return String.fromCharCode(0x30A0 + round(random(96)));

  return symbols[floor(random(symbols.length))];

}

​