This is a very emotional game! I love it!! The player speed does increase as the game progresses so it does add some variability to the game. I have some feedback / comments for you:
1) It would be super cool to have the background change while you are progressing to tell some sort of a story. Like the background becomes more red to indicate a more impending doom or something.
2) Im not sure if im seeing it but, it would be nice if the animation of the bird flaps faster as the game progresses which may give a sense of urgency?
Thanks for the feels-trip man. It was wild!!