Basics #4 in Scala

import org.lwjgl.LWJGLException
import org.lwjgl.{Sys => LWJGLSys}
import org.lwjgl.input.Keyboard
import org.lwjgl.opengl.{Display, DisplayMode}
import org.lwjgl.opengl.GL11._

object TimerExample {

  var x: Float = 400
  var y: Float = 300
  var rotation: Float = 0

  var lastFrame: Long = getTime()

  var fps: Int = 0
  var lastFPS: Long = getTime()

  def start() : Unit = {
    try {
      Display.setDisplayMode(new DisplayMode(800,600))
      Display.create()
    } catch {
      case e: LWJGLException => {
        e.printStackTrace()
        sys.exit(1)
      }
    }

    initGL()
    getDelta()
    lastFPS = getTime()

    while (!Display.isCloseRequested()) {
      val delta = getDelta()

      update(delta)
      renderGL()

      Display.update()
      Display.sync(60)

    }

    Display.destroy()

  }

  def update(delta: Int) : Unit = {
    rotation += 0.15f * delta
    if (Keyboard.isKeyDown(Keyboard.KEY_LEFT)) x -= 0.35f * delta
    if (Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) x += 0.35f * delta
    if (Keyboard.isKeyDown(Keyboard.KEY_DOWN)) y -= 0.35f * delta
    if (Keyboard.isKeyDown(Keyboard.KEY_UP)) y += 0.35f * delta

    if (x < 0) x = 0
    if (x > 800) x = 800
    if (y < 0) y = 0
    if (y > 600) y = 600

    updateFPS()
  }

  def getDelta() : Int = {
    val time = getTime()
    val delta =  time - lastFrame.toLong
    lastFrame = time
    delta.toInt
  }

  def getTime() : Long = {
    (LWJGLSys.getTime() * 1000) / LWJGLSys.getTimerResolution()
  }

  def updateFPS() : Unit = {
    if (getTime() - lastFPS > 1000) {
      Display.setTitle("FPS: " + fps)
      fps = 0
      lastFPS += 1000
    }
    fps += 1
  }

  def initGL() : Unit = {
    glMatrixMode(GL_PROJECTION)
    glLoadIdentity()
    glOrtho(0, 800, 0, 600, 1, -1)
    glMatrixMode(GL_MODELVIEW)
  }

  def renderGL() : Unit = {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)

    glColor3f(0.5f, 0.5f, 1.0f)

    glPushMatrix()
    glTranslatef(x,y,0)
    glRotatef(rotation, 0f, 0f, 1f)
    glTranslatef(-x, -y, 0)

    glBegin(GL_QUADS)
    glVertex2f( x - 50, y - 50 )
    glVertex2f( x + 50, y - 50 )
    glVertex2f( x + 50, y + 50 )
    glVertex2f( x - 50, y + 50 )
    glEnd()
    glPopMatrix()

  }

  def main(args: Array[String]): Unit = {
    start()
  }

}