//screen controls
var screen = 1;
var back = createSprite(200, 200);
back.setAnimation("welcome");
fill("white");
textSize(30);

//game sprites
var ufo = createSprite(0, 500);
ufo.setAnimation("ufo");
ufo.scale = 0.2;
ufo.velocityX = 0;
ufo.velocityY = 0;
var powerUp = createSprite(0, 500);
powerUp.setAnimation("powerupYellow_bolt_1");
var astro = createSprite(0, 500);
astro.setAnimation("sticker_34_1");
astro.scale = 0.3;
createEdgeSprites();

//game variables
var timer = 500; //time to rescue
var fuel = 5; //fuel remaining

function draw() {
  //button to move between screens
  if (keyWentDown("q")) {
    if (screen == 1) {
      //if on screen 1, move to #2-rules
      screen=2;
      back.setAnimation("rules");
    } else if ((screen == 2)) {
      //if on screen 2, move to #3-game
      screen=3;
      back.setAnimation("background");
      startGame();
    } else {
      //if on screen 4 or 5, restart 
      //move to #1-welcome
      screen=1;
      back.setAnimation("welcome");
      endGame();
    }
  }
  drawSprites();
  //if on game screen, play game
  if(screen==3){
    playGame();
  }
}
function startGame(){
  //move all sprites up from holding area to screen
  ufo.velocityX=-4;
  ufo.velocityY=4;
  ufo.x=320;
  ufo.y=120;
  astro.x=100;
  astro.y=200;
  powerUp.x=350;
  powerUp.y=300;
  fuel=5;
  timer=500;
}
function endGame(){
  //move all sprites down to screen 3 holding area
  ufo.velocityX=0;
  ufo.velocityY=0;
  ufo.x=0;
  ufo.y=500;
  astro.x=0;
  astro.y=500;
  powerUp.x=0;
  powerUp.y=500;
}
function playGame(){
  //move astronaut
  if (keyDown("up")) {
    astro.y -= 5;
  } else if ((keyDown("down"))) {
    astro.y += 5;
  } else if ((keyDown("left"))) {
    astro.x -= 5;
  } else if ((keyDown("right"))) {
    astro.x += 5;
  }
  //ufo movememnt & collison (lose fuel)
  ufo.bounceOff(edges);
  if (ufo.isTouching(astro)) {
    fuel--;
    ufo.x=350;
    ufo.y=350;
  }
  //pick up fuel
  if (astro.isTouching(powerUp)) {
    fuel++;
    powerUp.x=randomNumber(25, 375);
    powerUp.y=randomNumber(25, 375);
  }
  
  //handle time passing
  timer--;
  //if the time is done, you win
  if(timer<=0){
    //move to screen #4-win
    //move off the game sprites
    back.setAnimation("win");
    screen=4;
    timer=500;
    endGame();
  }
  
  //if the fuel is done, you lose
  if(fuel<=0){
    //move to screen #5-lose
    //move off the game sprites
    endGame();
    back.setAnimation("gameOver");
    screen=5;
  }
  //update fuel and time on screen
  text("Fuel: "+fuel+" Time to Rescue: "+timer,15,30);
}