For one person's work, this is pretty impressive; I certainly wouldn't be able to program/code the game, create artwork AND music in one weekend!
As constructive feedback/thoughts for future development, there's not much here in terms of originality of gameplay; it's a pretty standard 'collect the thing' platformer with a level timer added to fit the limitation. I like that the platform appears once you've collected the battery; if you were going to create more levels, I'd lean into that element of a 'there and back again' game, where the level has changed in interesting ways on the way back.