Beautiful sky! I'm amazed with how the colors change, in both the sea and the sky. I really like the detail in the clouds, only caught that later.
Only have 2 negative things to say (hope it is constructive):
(1) I think the lighthouse's light is a big problem. It doesn't look very good (too strong), and seems such as important effect to nail, since it is towards the "end" of the game (assuming people will play through once to see everything). Sticks out a lot in an otherwise great looking place.
(2) I think you should relocate the upper door of the light-house, or adjust the music? I like the build-up, but it would be much better if the "climax" happened when the player looked through the door at the world. As it is, it happens when he reaches the top of the staircase, but only looking at a wall.
Very nice job overall, though. I'm still opening the game just to look at the sky every now and then! Good luck in future projects. :)