It was truly a pleasure to play this game: an excellent idea and very well executed.
For quick and simple improvements, I would add a pause button to the game. Also, it took me a while to realize what the line at the top of the screen represented since I always have my focus on the character. I would make it so that when the character reaches the gateway to heaven, a cloud appears above them, and they rise up to it to disappear. Additionally, I would bring the camera closer to the level to improve visibility on smaller screens.
Best of luck with it!