itch.io

You unlock the Windmill when you create the Shovel. I've only found 3 things in the Windmill build menu (Animal Feed, Wheat Seeds, and Tree Saplings) and they were there from creation of the Windmill. 

You can destroy every structure (except the Marketplace, unless I haven't figured it out) by smacking it with your pickaxe. The structures that build things must be in the process of building something and then you can smack it til it breaks before it finishes the build. You receive all of the materials it took to create the structure in the first place, so don't worry about losing the materials. However, I have discovered that if you destroy a Furnace while it is making something using Coal, the Coal will not be returned. Lost 64 coal canceling Gold Ingots :(

I agree with literally every point here. I am already in love with this game and can not wait for it to release in full. I'm not as far as OP, looking at around 2.5 hours and maybe 5-6 islands unlocked at Level 12.