omg, you did that being 11? that's impresive! the game is fun, and it works properly.
just a few things:
1- there's no point in saving energy balls (it would make more sense if the time you rewind the aliens would be bigger if you have more energy balls)
2- collisions are a bit too big or something, like... if you colide with small branches in the floor, they souldn't stop you etc...
3-add a bit more randoomness, if you can at some point, like... where the energy balls spawn or the level layout
4- this one is very tiny, some trees are floating hehe.
Congratulations, it's a nice game!