Wow I got to go to the Bahamas wohoooooo!!!
Ok wow am I actually really surprised by this game. When the tutorial came up, there were many writing errors and I thought "oh boy, that's gonna be a bad game". But wow the game proved me wrong. While I didn't try out the shotgun I think the shooting felt quite good and I had fun killing those undead! The variation with big zombies was also good.
But what I really liked was the round-to-round approach where you have to select a mission every day and then you can play another round. Made it feel like some kind of zombie mode (it kinda is huh?:D) Also very interstingly we both have the same idea for the theme implementation where after more time passes more enemies will come. Cool!
Some things I think you could improve on: Having to use the mouse to select between night and the dealer was kind of a struggle. It would have been nice to have a menu popup when you press a certain key near the gate I think. Also my mouse keeps going out of the fullscreen window, don't know if this is your bug or unity but it was also annoying.
Other than that great game, I really liked it! If you don't mind please check out my game: https://ldjam.com/events/ludum-dare/40/just-another-space-game