centipede arcade game for vid screens in Cryptovoxels (WIP)

centipede.js

let player, frame, bullets, mushrooms

// main loop functions

feature.on('keys', e => {
  if (!player) { return }
  
  if (e.keys.left) {
    player.xVel = -1
  } else if (e.keys.right) {
    player.xVel = 1
  } else {
    player.xVel = 0
  }
  
  if (e.keys.up) { 
    player.yVel = -1
  } else if (e.keys.down) {
    player.yVel = 1
  } else {
    player.yVel = 0
  }
    
  if (e.keys.a) {
    if (bullets.length == 0 || frame - bullets[bullets.length - 1].timeBorn > 3) {
      player.shoot()
    }
  }
})

feature.on('start', e => {
  reset()
})

feature.on('frame', e => {
  frame += 1
  update()
  draw()
})

function update() {
  player.update()
  
  let inactiveBullets = []
  for (let i = 0; i < bullets.length; i ++) {
    bullets[i].update()
    if (!bullets[i].active) {
      inactiveBullets.push(i)
    }
  }
  for (let i = 0; i < inactiveBullets.length; i ++) {
    bullets.splice(inactiveBullets[i] - i, 1)
  }
  
  let deadMushrooms = []
  for (let i = 0; i < mushrooms.length; i ++) {
    if (mushrooms[i].health <= 0) {
      deadMushrooms.push(i)
    }
  }
  for (let i = 0; i < deadMushrooms.length; i ++) {
    mushrooms.splice(deadMushrooms[i] - i, 1)
  }
}


function draw() {
  feature.screen.fill(0)
  player.draw()
  for (let i = 0; i < bullets.length; i ++) {
    bullets[i].draw()
  }
   
  for (let i = 0; i < mushrooms.length; i ++) {
    mushrooms[i].draw()
  }
}

function reset() {
  frame = 0
  player = new Player(30, 58)
  bullets = []
  
  mushrooms = []
  for (let i = 0; i < Math.round(Math.random() * 20) + 5; i ++) {
    mushrooms.push(new Mushroom(2 * Math.round(Math.random() * 31), 2 * Math.round(Math.random() * 26)))
  }
  
  draw()
}

// helper functions

function drawPixel(x, y, rgb) {
  if (rgb.length != 3) { return }
  
  for (let z = 0; z < rgb.length; z ++) {
    feature.screen[y * feature.screenWidth * 3 + x * 3 + z] = rgb[z]
  }
}

function drawBlock(x, y, rgb, size) {
  for (let u = 0; u < size; u ++) {
    for (let r = 0; r < size; r ++) {
      drawPixel(x + u, y + r, rgb)
    }
  }
}

// classes

class Player {
  constructor(x, y) {
    this.xPos = x
    this.yPos = y
    this.xVel = 0
    this.yVel = 0
    this.size = 4
  }
  
  shoot() {
    bullets.push(new Bullet(this.xPos + 1, this.yPos - 1))
  }
  
  update() {
    if (frame % 2 != 0) {
      return
    }
    
    let nextX = this.xPos + this.xVel
    let nextY = this.yPos + this.yVel
    
    // wall collision detection
    
    if (nextX >= 0 && nextX <= 63 - this.size + 1) {
      this.xPos += this.xVel
    }
    if (nextY >= 0 && nextY <= 63 - this.size + 1) {
      this.yPos += this.yVel
    }
  }
  
  draw() {
    drawBlock(this.xPos, this.yPos, [150, 255, 140], this.size)
  }
}

class Bullet { 
  constructor(x, y) {
    this.xPos = x
    this.yPos = y
    this.size = 2
    this.yVel = -2
    this.timeBorn = frame
    this.active = true
  }
  
  update() { 
    this.yPos += this.yVel
    
    if (this.yPos < 0 - this.size) {
      this.active = false
    }
    
    // detect collision with mushroom
    
    if (mushrooms) {
      for (let i = 0; i < mushrooms.length; i ++) {
        let nextY = this.yPos + this.yVel
        let mushroom = mushrooms[i]
        if (nextY >= mushroom.yPos && nextY < mushroom.yPos + mushroom.size - 1 
           && this.xPos >= mushroom.xPos - 1 && this.xPos < mushroom.xPos + mushroom.size) {
          this.active = false
          mushroom.health -= 1
        }
      }
    }
  }
  
  draw() {
    drawBlock(this.xPos, this.yPos, [255, 255, 255], this.size)
  }
}

class Mushroom {
  constructor(x, y) {
    this.xPos = x
    this.yPos = y
    this.size = 4
    this.colour = [240, 240, 10]
    this.health = 3
  }
  
  draw() {
    if (this.health == 3) {
      drawBlock(this.xPos, this.yPos, this.colour, this.size)
    } else if (this.health == 2) {
      for (let i = 0; i < this.size; i ++) {
        drawPixel(this.xPos + i, this.yPos, this.colour)
        drawPixel(this.xPos + i, this.yPos + this.size - 1, this.colour)
        if (i >= 1 && i < this.size - 1) {
          drawPixel(this.xPos, this.yPos + i, this.colour)
          drawPixel(this.xPos + this.size - 1, this.yPos + i, this.colour)
        }
      }
    } else if (this.health == 1) {
      for (let i = 1; i < this.size - 1; i ++) {
        drawPixel(this.xPos + i, this.yPos, this.colour)
        drawPixel(this.xPos + i, this.yPos + this.size - 1, this.colour)
        drawPixel(this.xPos, this.yPos + i, this.colour)
        drawPixel(this.xPos + this.size - 1, this.yPos + i, this.colour)
      }
    }
  }
}