Hi, I'm the dude from the comment section that suggested a cat-skull truck as a mini-boss for completing a "Small, Unimpressive Fort" side-quest.

-But I'm not here to stroke my ego, I'm here to share some stuff I found on the internet and I have found some stuff!

• LD - In pursuit of better levels - Google Docs This google doc is quite a fine one- for FPS games mainly - I still recommend it for a good read and structural inspiration, along with how it goes into enemies and how to make the feel right (one example from the doc is pushing back a part of a t-junction to make a cover spot and direct the player's attention better than a 50/50 of left or right.) I have to say it is at least a well formatted essay on google docs (which is at the very least- tedious).
• The Problem with Noitas Secrets Even though this youtube video shows the "problems" with another game's puzzles, I feel like it invites a nice idea (mainly in the comments of the video) of having puzzles for the community rather than the single player, I feel like doing some puzzles like this might help satiate people's wanting for multiplayer, or just be a fun thing to do/look forward too.
• Three Musical Youtubers:
  • Samwow - A person who just got done with doing a soundtrack for his and his friend's game, I think he does really good work that has a consistent thematic tone, though his regular stuff is probably not what you are wanting your game to bring.
  • Oliver RGN - My oh my, does this dude do some really well made chiptune remixes. They're different yet keep the same feeling as the original! You may want to contact him to perhaps add a feature where if you do the pixelation (pixellation?) to a certain level it starts doing tracks in the game remixed into chiptune.
  • Larner Music - This gentleman has only 4 subscribers, which is most complexing due to having amazing music- and perhaps the best music for the "Cat-skull truck that has a scoop" mini-boss there is - because This video would be upmost great for it, and at the minute and a half mark it goes into a great brisk beat that is just something I feel could already be lurking in the game! (I actually found this video quite a while ago but I just now put 2-and-2 together) He also has an itch.io so he is probably the easiest to contact.
•  Random News Company Name Generator - this is really nothing, but it is funny to put "Dummo" in it and get a long list of "potential news company names" that sound really, really, dumb; you might be able to use/base some code off of this to add a radio station that constantly changes it's name except for some specific word.

I hope that these interest you (at least partially) and helps with updating or planning for the game!

Now onto the first of the title of this post, improving my idea of the skull-cat truck and the "Berkly's small unimpressive fort" side mission to fight it. I feel like getting shovels parts may be a good idea for it to end at a tomb in one of the forts - of course this tomb would be tiny, small, and unimpressive - though only a "golden shovel" could dig it up. These golden shovel parts could be found in other  Berkly forts due to him only having the gold shovel to flaunt his wealth (so he divided it up between them all to have something for every fort).

Here is my idea for the quest and stuff in it (feel free to completely ignore this though, you probably thought of something much better)

• The Four Forts:
  • "Berkly's Small Unimpressive Outpost" could show up nearer to the player's starting place and have the stick/middle part of the golden shovel, with a note like "Do not steal - Berkley" this stick could then point to other parts of the shovel like a dowsing stick
  • "Berkly's Small Unimpressive Keep" This is were you could first meet berkly sleeping on a bed larger than the inner fort, with the shovel lower's handle in a ditch next to one of the keep's walls, along with some skeletons (possibly with cat ears to hint to the upcoming miniboss?)
  • "Berkly's Small Unimpressive Fort" is where you get the shovel's golden blade. The fort would look similar to the keep, but would have a chimney in it that you would go down in to get to the room with the blade. It could have three main rooms with a dining room, a dance hall, and a throne room. All of these rooms would have some fancy looking drapery's but the furniture would all be small wooden chairs and stools, the throne could be a wooden chair with a cushion on it. Once you get the shovel blade from the throne room and go back to the exit (fighting skeletons along the way) Berkly could end up back in his fort with you (presumably) getting rid of the skeletion's in his fort. Though he could just break the chimney and have a campfire along with his previous bed on the outside of the fort.
  • "Berkly's Small Unimpressive Tomb" Is where you can start the mini-boss after getting the shovel fixed up by Hogan. The surrounding area could have a parking lot (more foreshadowing) with the same low walls as the other three buildings and tinier gravestones than the starting area, with one slightly bigger golden grave stone with cat ears. You dig it up with the shovel and the fight starts with an explosion and a truck horn!
• Berkly could be construction worker with tiny hands, explaining the small structures
• Cat ears could grant larger arm power, because cats claw stuff
• Mini-boss fight music could be like the video I linked by Larner Music
• The Mini-boss could mow-down the small tomb area, leaving it to charge at you in an open field
  • Another attack could be throwing the scoop at you, though it may be hard to code it to pick it back up (though it could probably regrow another)
• The purpose of going to the tomb area could be to get a debuff off the shovel "like curse of the cat-truck" or something that sounds better than "cat-truck curse"
  • Could also be used to learn a "charge" move (because I seen on other post about you adding "spin" moves to learn and such)

That's really all from me without getting (super) nit-picky of how the quest could play out. Thank you again for even considering something I wrote down for this awesome game- it really makes me proud that you found skull-cat-truck a cool idea.

(also seen those flying enemies in that video and it is just plain evil, yet fun and engaging, of you to add that)