What a fun playthrough, great job mate!!! The 40-45 hours of dev time really paid off, everything feels well polished and the game loop is complete. The city layout is great feels very realistic and the aesthetic effects of switching to night time (darker lighting, black marks on the ground) really sell the upside down feel. You did a good job of arranging all the models, to the point it doesn't even feel like you used an asset pack.
The combat is really fun and there's a impressive amount of depth for a week jam. There were some real intense MOB-style fights where I was mashing around on my keyboard desperately trying to stay alive, 5/5 on gameplay/engagement for me. Looting around for weapon upgrades between waves was a great design decision and not only gave a much needed breather between the action but also helped emphasize the danger of the upside down. The boss fight at the end was a nice cherry on top too. SFX/music worked really well for the jam; if you keep developing the game some more sfx for weapons/enemies/etc would be nice too.
The only real criticism I have is the lack of a mini-map (understandable for a jam time frame) leading to me getting lost in the city quite a bit. Especially looking for the portal between rounds. It was fun to explore the city looking for upgrades but I think something like a little compass arrow on the side pointing to the portal would have been a much appreciated quality of life change. This was probably my favorite entry in the jam so far, awesome work and keep it up!!
edit: also like another comment said the game wouldn't run on Firefox for me, but did run on Microsoft Edge no problem