Overview

I have a scene manager in my game and in each 'Scene' I have a render() and a update() method for drawing and updating my game's logic.

Basically, when I want to switch to another scene, let's say, when the player progresses to the next level or going from game-over back to the main menu, I just do something like this:

SceneManager.getInstance().setCurrentScene(level2); //Where level 2 is a 'Scene' class.

I have a 'MainGame' scene who's sole purpose is to house all the methods I call from my individual levels. So I might then do something like this:

Current method

public class Level1 extends MainGame implements Scene {

    private Resources res;
    private MyGLRenderer r;

    Level1(MyGLRenderer r, Resources res){
        super(r, res);
        this.res = res;
        this.r = r; 
    }

    @Override
    public void render() {      
        draw(background);
        draw(playerSprite);
        draw(blue-enemies);
    }

    @Override
    public void update(){
        super.movePlayer();
        super.moveEnemies();
        super.checkCollision();
    }

}

However, in my game, when the player survives for a certain amount of time, I want to introduce more elements into the game, so I might then have a 'level2' Scene (although strictly, from the player's perspective, the game is perceived to be one big rolling level).....

    public class Level2 extends MainGame implements Scene {

        private Resources res;
        private MyGLRenderer r;

    Level2(MyGLRenderer r, Resources res){

        super(r, res);
        this.res = res;
        this.r = r; 
    }

    @Override
    public void render() {      
        draw(background);
        draw(playerSprite);
        draw(blue-enemies);
        draw(pink-enemies);  //New!!!! *********************************
    }

    @Override
    public void update(){

        super.movePlayer();
        super.moveEnemies();
        super.checkCollision();
    }

}

So, as you can see, Level2 is exactly the same as Leve1 but now I'm also drawing my 'pink-enemies', I can keep doing this for 'levels' 3 through 10 but I'll end up duplicating and simply adding to each level each time. Seems like a lot of effort just to introduce 1 or 2 new things every 'level'.

Using conditions within my render / logic?

Is there a cleaner / tidier way of achieving that which I'm trying to achieve? I could do away with all my individual 'Level' classes altogether and just work straight out my MainGame class's Render() and Update() methods, but then I would have to have something like:

Render(){

    //Render elements common to all levels
    draw(background);
    draw(playerSprite);
    draw(blue-enemies);

    //Render specific level objects
    
    Switch (Level){

        case 4:{draw(giantAlienSpaceship);}
        case 3:{draw(orange-enemies);}
        case 2:{draw(pinkEnemies);break;}
    }
}

And then a similar switch in my logic. I'm not sure about this however, as it adds additional switch/conditional statements in my rendering and seems somewhat 'amateur' however, I could be completely wrong and this may be an acceptable method that people do use.

Am I missing any other obvious cleaner / cleverer way to do this (similar to my first method but without the duplicated super method calls)