Looks really imaginative. It almost reminds of Truman Show, where the sky/ocean opens into a hidden platform 
Enjoy it!
Couldn’t stop playing around… but enough of that, I’m sure most of this is horrible practice… so back to the course!
Looks like it’s coming along very nicely. I don’t see it as horrible practice. you have some obstacles to test different parts of navigation and combat mechanics as you go along. Plenty of space to test many different scenarios. And just a touch of texture to provide interest to the play area as well as inspiration as your move along. All and all very nicely done. Look forward to seeing how it develops.