I really wish you could just buy multiple power ups of the same type. Even if you had to use them before you could purchase different powerups, I'd be cool with that since I only use the same 3 anyway.
There needs to be a bullion exchange. Something like 5k coins per 1 bullion exchange rate so it isn't so luck dependent. I've already 3 starred every mission and I still have 1 empty slot and no final ship because I'm still saving bullion. I'm just going to quit the game, what else is there besides grinding to get bullion at this point?
"I think that part of the preface of the game should explain that a rushing underground river was discovered, and that is being used to turn a gear which is to be used to turn the windmill which is used to power the town... (instead of just directly powering the town itself...) Solar alternative much?" - Developer
Then they should have made use of hydroelectricity, they're most the way there already. Is this the village Rube Goldberg came from?