let player;

let bullets = [];

let viruses = [];

let score = 0;

​

function setup() {

  createCanvas(600, 400);

  player = new Player(width / 2, height / 2);

​

  // Spawn initial viruses

  for (let i = 0; i < 5; i++) {

    spawnVirus();

  }

}

​

function draw() {

  background(0);

​

  // Update and display player

  player.update();

  player.display();

​

  // Update and display bullets

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

    bullets[i].update();

    bullets[i].display();

​

    // Check bullet collision with viruses

    for (let j = viruses.length - 1; j >= 0; j--) {

      if (bullets[i].hits(viruses[j])) {

        bullets[i].remove();

        viruses[j].remove();

        score++;

        break;

      }

    }

  }

​

  // Remove bullets and viruses

  bullets = bullets.filter(bullet => !bullet.isOffscreen());

  viruses = viruses.filter(virus => !virus.isOffscreen());

​

  // Spawn new viruses

  if (random(1) < 0.01) {

    spawnVirus();

  }

​

  // Display score

  fill(255);

  textSize(20);

  text('Score: ' + score, 10, 30);

​

  // Check player collision with viruses

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

    if (player.hits(viruses[i])) {

      gameOver();

      return;

    }

  }

}

​

function keyPressed() {

  if (keyCode === UP_ARROW) {

    player.move(0, -1);

  } else if (keyCode === DOWN_ARROW) {

    player.move(0, 1);

  } else if (keyCode === LEFT_ARROW) {

    player.move(-1, 0);

  } else if (keyCode === RIGHT_ARROW) {

    player.move(1, 0);

  } else if (key === ' ') {

    bullets.push(new Bullet(player.x, player.y));

  }

}

​

function spawnVirus() {

  let side = floor(random(4));

  let x, y;

​

  if (side === 0) {

    x = random(width);

    y = -20;

  } else if (side === 1) {

    x = width + 20;

    y = random(height);

  } else if (side === 2) {

    x = random(width);

    y = height + 20;

  } else {

    x = -20;

    y = random(height);

  }

​

  viruses.push(new Virus(x, y));

}

​

function gameOver() {

  textSize(32);

  textAlign(CENTER, CENTER);

  fill(255);

  text('Game Over', width / 2, height / 2);

  noLoop();

}

​

// Player class

class Player {

  constructor(x, y) {

    this.x = x;

    this.y = y;

    this.speed = 3;

    this.size = 20;

  }

​

  update() {

    this.x = constrain(this.x, 0, width - this.size);

    this.y = constrain(this.y, 0, height - this.size);

  }

​

  display() {

    fill(0, 255, 0);

    rect(this.x, this.y, this.size, this.size);

  }

​

  move(xDir, yDir) {

    this.x += xDir * this.speed;

    this.y += yDir * this.speed;

  }

​

  hits(virus) {

    return (

      this.x < virus.x + virus.size &&

      this.x + this.size > virus.x &&

      this.y < virus.y + virus.size &&

      this.y + this.size > virus.y

    );

  }

}

​

// Bullet class

class Bullet {

  constructor(x, y) {

    this.x = x;

    this.y = y;

    this.speed = 5;

    this.size = 5;

  }

​

  update() {

    this.y -= this.speed;

  }

​

  display() {

    fill(255);

    ellipse(this.x, this.y, this.size);

  }

​

  isOffscreen() {

    return this.y < 0;

  }

​

  hits(virus) {

    return (

      this.x > virus.x &&

      this.x < virus.x + virus.size &&

      this.y > virus.y &&

      this.y < virus.y + virus.size

    );

  }

​

  remove() {

    this.x = -100;

    this.y = -100;

  }

}

​

// Virus class

class Virus {

  constructor(x, y) {

    this.x = x;

    this.y = y;

    this.speed = 2;

    this.size = 30;

  }

​

  update() {

    let dx = player.x - this.x;

    let dy = player.y - this.y;

    let angle = atan2(dy, dx);

    this.x += cos(angle) * this.speed;

    this.y += sin(angle) * this.speed;

  }

​

  display() {

    fill(255, 0, 0);

    rect(this.x, this.y, this.size, this.size);

  }

​

  isOffscreen() {

    return (

      this.x < -this.size ||

      this.x > width ||

      this.y < -this.size ||

      this.y > height

    );

  }

​

  remove() {

    this.x = -100;

    this.y = -100;

  }

}

​

​

​

​