Hello,
Wow, what a great game! You just nailed it in every aspect. Progression, enemies, level design, upgrades, music. One of the best games out of the 50 entries I have played so far, congratulations!
As a minor detail, I ended up fearing every corner and ceiling because those spiders fall from above at random points as I understood. I would have loved some clearer visual information to understand where they come from so that I can anticipate their randomness. Something like the flowers in Super Mario: they always come from green pipelines, but not from all of them, and this lets me anticipate potential danger.
Again, well done!
PS: try to find the sequence break in our game :D