Overall : The idea is great, I love the kind of silly vibe: farming, aliens, and a grappling hook, just had a sort of tongue in cheek feel that it didn't take itself too seriously which made it just feel more relaxed and fun. The grappling hook is smoooth, very nice. The gun could use some additional fx/work but it pushing you back is a great detail, makes it feel stronk. Also the minimap is essential for this kind of game where you are defending a large area with multiple points of interest, if you didn't have that it would be frustrating. Getting that feature in was super important so great work with that.
The aliens lunging at you when you get close is cool, they remained kinda scary even after I knew how to time my shots. I think with the way the shotgun behaves it makes it sort of a timing game if you kill one without getting hit, which is good. I'm pretty sure the only reason it can be annoying is the camera - when the player is walking in a direction, the camera smooth makes it so you know less about what you're walking into than what's behind you. I think Natedog's idea about using the mouse to look around might be worth trying out. On the subject of aliens, some green blood could make them funner to shoot, or if you wanted to keep it cutesy you could give them a little jitter and knockback when shot, before they die.
The main issue though is there isn't really anything to work towards, which is probably due to jam time constraints of course. But I'm gonna make some suggestions anyway because this game gives me ideas lol
You should probably require crops to progress in the game/survive, in some fashion or another since they aren't useful now. My personal idea is that the game could be divided into months, each month is like a "round" in the game. The round of gameplay has a time limit, and each month you eat X amount of food. When winter rolls around, maybe you can't grow crops for 3 rounds and this is sort of the big scary thing you need to hoard extra crops for. I think this would be great coupled with the ability to trade/sell food for upgrades. This would require the player to gamble on themselves. "Can I really afford to upgrade my grappling hook? It will make getting around easier but I'll have less of a safety net for the next winter". So Spring would feel kinda safe and lighthearted, la dee da I survived the winter and I have 9 months till next winter, I can buy cool shit at the store I ain't scared" and then fall rolls around and you're like "ohmygod I need more food I'm gonna die this winter why did I buy that cool hat"
There are a million ways you could do it though, that was just my armchair game design thoughts. This game was funny and unique, I gave 3 or 4 stars in my rating. Great work!