Nice game! I liked that the motivation changed halfway through. It was a nice story point. Also, I have no idea how you created the main character from the sprite pack ... or maybe you didn't! Either way, you used everything really well, especially to make the sand and water.
I liked your intro UI as well. Everything felt very clean and thoughtful in your design.
I also liked how the music tempo increased as the wall of pollution got closer! Dynamic music is always a cool thing. Maybe you could have set it back to a nice slow tempo on the end screen, though :) Great job!