looks like you are going all in with the game and i really think you should.
when i played it in the first time it was really fun and i am sure that after all of the updates you are doing it will be even way more better.
i saw you really like and listen to the thoughts of your players so here are mine:
- about the multiplayer, multiplayer is almost always a really fun feature, you can do so you and your friend and you are starting to build the bridge together and fighting agains a bigger storm. maybe, if you can do so two players can play on one screen.
OR
you can do so you play against an another guy and using the planes you can attack and steal to the other player resources.
or just do both if you can.
- forgive me if you already did this and i didnt notice but you should do so you can move the buildings from place to place after building them.
- for the achivments you can do the basic idea of giving badges and add a style to the bridge it self (make an each style for an each achivment)
good luck with adding all of the features, waiting to see them(you can be sure i will see them because i followed you).
seriouslly by how it looks for now to me it looks like a game that has so much future and looks like you noticed it by (actually if you ask me the game is already very very good).