let aliens = [];

let pews = [];

let score, startFrame;

let gameover;

​

function preload() {

  bg = loadImage("bg.png");

  sprites = loadImage("sprite_sheet.png");

}

​

function setup() {

  createCanvas(300, 400);

  bg = loadImage("bg.png");

  phage = new Phage();

  for (let i = 0; i < 18; i++) {

    aliens[i] = new Alien(10 + (i % 6) * 40, 120 + int(i / 6) * 40);

  }

  gameover = false;

  score = 0;

  pews = [];

}

​

function draw() {

  imageMode(CORNER);

  background(bg);

​

  if (!focused) {

    fill(255);

    textAlign(CENTER, CENTER);

    textSize(30);

    text("Click to start", width / 2, height / 2);

    textSize(20);

​

    text("LEFT/RIGHT: move\nUP: shoot", width / 2, (3 * height) / 4);

    startFrame = frameCount;

    return;

  }

  if (!gameover) {

    if (keyCode === LEFT_ARROW) {

      phage.move(-5);

    } else if (keyCode === RIGHT_ARROW) {

      phage.move(5);

    }

  } else {

    fill(255);

    textAlign(CENTER, CENTER);

    textSize(30);

    text("Score: " + score, width / 2, height / 2);

    textSize(20);

    text("Type ' r ' to restart", width / 2, (3 * height) / 4);

    startFrame = frameCount;

  }

  phage.display(gameover);

​

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

    aliens[i].move();

    aliens[i].display(i % 6, int(i / 6));

  }

​

  for (let i = pews.length - 1; i >= 0; i--) {

    pews[i].display();

    if (pews[i].y < 30 || pews[i].hasHit) pews.splice(i, 1);

  }

​

  textSize(30);

  textAlign(RIGHT, CENTER);

  if (!gameover) {

    text("" + score, (19 * width) / 20, height / 10);

    if (score == 18) {

      fill(255);

      textAlign(CENTER, CENTER);

      textSize(30);

      text("You Win!", width / 2, height / 2);

      textSize(20);

      text("Type ' r ' to restart", width / 2, (3 * height) / 4);

    }

  }

}

​

class Alien {

  constructor(x, y) {

    this.x = x;

    this.y = y;

    this.gamespeed = 0.4;

    this.died = -1;

  }

​

  move() {

    if ((((frameCount - startFrame) % 100) * 0.4) / this.gamespeed == 0) {

      this.gamespeed *= -1;

      this.y += 3;

    }

    this.x += this.gamespeed;

    this.y += 0;

    this.y = min(this.y, height - 20);

  }

​

  display(row, col) {

    if (this.died < 0) {

      image(sprites, this.x, this.y, 48, 48, 24 * (2 - col), 0, 24, 24);

    } else {

      if (frameCount - this.died < 30 && frameCount % 10 < 5) {

        image(sprites, this.x, this.y, 48, 48, 24 * (2 - col), 24, 24, 24);

      }

    }

  }

}

​

class Phage {

  constructor() {

    this.x = random(width);

    this.y = 330;

    this.gamespeed = 1;

  }

  move(d) {

    this.x += d;

    this.x = constrain(this.x, 20, width - 10);

  }

  display(over) {

    push();

    translate(this.x, this.y);

    scale(1, 1.0 - 2 * over);

    imageMode(CENTER);

    image(sprites, 0, 0, 48, 72, 24, 48, 24, 36);

    pop();

​

    for (let i = aliens.length - 1; i >= 0; i--) {

      if (

        aliens[i].died < 0 &&

        dist(this.x, this.y, aliens[i].x, aliens[i].y) < 80

      ) {

        gameover = true;

      }

    }

  }

}

class Pew {

  constructor(x) {

    this.x = x;

    this.y = height - 100;

    this.gamespeed = -2.5;

    this.hasHit = false;

  }

​

  display() {

    this.y += this.gamespeed;

    fill(255, 255, 0);

    textAlign(CENTER, CENTER);

    textSize(20);

    text("|", this.x, this.y);

    for (let i = aliens.length - 1; i >= 0; i--) {

      if (dist(this.x, this.y, aliens[i].x + 24, aliens[i].y + 24) < 10) {

        if (aliens[i].died < 0) {

          aliens[i].died = frameCount;

          score++;

          this.hasHit = true;

        }

      }

    }

  }

}

​

function keyPressed() {

  if (keyCode === UP_ARROW) {

    if (pews.length < 6 && !gameover) {

      pews.push(new Pew(phage.x));

    }

  } else if (key === "r") setup();

}

​

function keyReleased() {

  keyCode = 0;

  return false;

}

​