inicializa scoreCounter asi: public Counter scoreCounter; luego para acceder a los métodos del contador, si quieres incrementar ; scoreCounter.add(); hasta ahí tienes el decremento tienes editar los métodos contenidos en la clase Counter y añadir uno nuevo; si quieres mas pistas te digo

Would I save the start location in World or in Mario?

Create two ints in the world. int marioStartX; int marioStartY; And then in the setupLevel you should remember to set these to the location that you add Mario to. Then you can create a reset method which set Mario's location to the start location. Though you can also add these ints to the Mario class, I doesn't really matter. So just put them where you have the easiest access to them when you need them.

It really depends on how much you want to reset, is it only Mario? is it Mario and enemies? is it Mario, enemies and coins? If it's only Mario, you can easily create a reset method which would look something like this: public void reset() { setLocation(marioStartX, marioStartY); } If you saved the integers in Mario. If you have them in the world the code would look like this: public void reset() { WorldClassNameHere world = (WorldClassNameHere) getWorld(); setLocation(world.marioStartX, world.marioStartY); }