Nice! Finished it, not sure what everyone is talking about in their spoilers below, but to me it felt like a proper ending, or at least, I was hoping for some 'pirate stuff', but this ending fits the game at least. Not sure about the secrets mentioned below either, haven't found any unfortunately.
But, all in all, good game!!! Nice atmosphere, nice linking together of the island puzzles. Felt fair mostly, think I was able to finish with only two times peaking below in the walkthrough vid, but only for some inspiration actually. Was able to figure it for myself mostly.
Anyway, to summarize: nice! Nice mechanics, nice atmosphere, nice puzzles, nice balance!