Working draw()

void draw()
{

  background(255);
  if (screen == 0)//main menu
  {
    image(photo,0,0);
  }
  else if (screen == 1)//Gamemodes
  {
    image(photo2,0,0);
  }
  else if (screen == 2)//How to play
  {
    image(photo3,0,0);
  }
  else if (screen == 4)//Credits
  {
    image(photo5,0,0);
  }
  else if (screen == -1) //settings menu
  {
    image(photo4,0,0);
  }
  else if (screen==5)
  {
    //chooseGameMode(1);
  }
  else if (screen ==6)
  {
  }
  else if (screen ==7)
  {
  }
    //Selected boxes for settings menu
  if (screen == -1)
  {
    if (a == 1)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(465,175,80,70);
    }
    else if (a == 2)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(583,180,65,63);
    }
    else if (a == 3)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(695,177,60,68);
    }
    if (b==1)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(350,280,350,43);
    }
    else if (b==2)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(40,368,360,40);
    }
    else if (b==3)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(440,367,320,40);
    }
    else if (b==4)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(440,445,300,40);
    }
    else if (b==5)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(20,443,370,40);
    }
    if (c==1)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(415,670,90,55);
    }
    else if (c==2)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(675,670,140,55);
    }
    if (d==1)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(425,823,90,55);
    }
    else if (d==2)
    {
      stroke(224,255,255);
      strokeWeight(3);
      noFill();
      rect(685,823,130,55);
    }
  }
  //actual game
   if(screen ==6)
   {
    fill(0);
    textSize(14);
    text("Score = " + g , 850,100);
    if (g>=best)
      best = g;
    strokeWeight(1);
    fill(0,255,0);
    text("Best = " + best, 850, 150);
   }
   else if(screen==8)
   {
    strokeWeight(1);
    fill(0,255,0);
    text("Best = " + best, 850, 150);
    gameOver=false;
   }
   else if(screen==7)
   {

   }
  //restart the game
  if (gameOver ==true && (screen == 6 || screen == 7 || screen == 8))
  {
    if(gameOver ==true && (screen == 6 || screen == 7 || screen == 8))
    {
    image (photo10,0,0);
    }
    if (restart)
    {
      gameOver = false;
      s1 = new Snake (10, "arrows");
      if (mode == 2)
      {
        s2 = new Snake(20, "wasd");
        s1.setOtherSnake(s2);
        s2.setOtherSnake(s1);
      }
      if (mode == 3)
      {
        s3 = new Snake(20, "computer");
        snakeAi = new ComputerSnake();
        s1.setOtherSnake(s3);
        s3.setOtherSnake(s1);
      }
      restart = false;
    }
  }
  //bracket
  if (mode == 1)
    {
      if(s1.drawSnake())
      {
        renderer.drawCollision();
        gameOver = true;
        g=3;
      }
      else
      {
        if (mode == 3)
        {
         renderer.drawBoardComputer();
        }
        if (mode == 2)
        {
          renderer.drawBoardMulti();
        }
        if (mode == 1)
        {
          renderer.drawBoardSingle();
          fill(0);
          textSize(14);
          text("Score = " + g , 850,100);
        }
      }
   }
   else if (mode == 2)
   {
     if(s1.drawSnake() || s2.drawSnake())
     {
       renderer.drawCollision();
       gameOver = true;
       g=3;
     }
     else
     {
       if (mode == 2) renderer.drawBoardMulti();
       if (mode == 1) renderer.drawBoardSingle();
     }
   }
   else if (mode == 3)
   {
     if(s1.drawSnake() || s3.drawSnake())
     {
       renderer.drawCollision();
       gameOver = true;
       g=3;
     }
     else
     {
       if (mode == 3) renderer.drawBoardComputer();
       if (mode == 2) renderer.drawBoardMulti();
       if (mode == 1) renderer.drawBoardSingle();
     }
   }

   //draw picture over powerup
   if (p.isAvailable == true)
   {
     if (p.choose == 1)
     {
       image(photo6,(p.x * 20.0), (p.y * 20.0));
     }
     if (p.choose == 2)
     {
       image(photo7,(p.x * 20.0), (p.y * 20.0));
     }
     if (p.choose == 3)
     {
       image(photo8,(p.x * 20.0), (p.y * 20.0));
     }
     if (p.choose == 4)
     {
       image(photo9,(p.x * 20.0), (p.y * 20.0));
     }
   }
}