Thank you so much for playing and the thorough feedback! I appreciate it!
One thing to note, green doesn't have a cap of ten, it's just that the maximum digits are 2 for the UI counter, so it seems like it's capped, especially on the easy level which is filled with bio tiles. The cap was supposed to be 99, it's currently uncapped.
Regarding balancing and content, you're spot on. Currently increasing the drill power and gathering a lot of dirt is the easiest way to deal with most bosses. The exception is the one in the hard level, which requires you to shield properly because it lashes out a lot of damage.
The reason for that was time, of all things haha. I realized I had to wrap up the game and iron out the kinks, so after I made etherdrill, sacriguard (useless) and sparklers (strongest if you don't focus on one particular stat), I was running out of time and still had to fix some things. I had two plans: one was to make stronger versions of elemental attacks that used less dirt, and the other was to put elements on enemies so attacks would be less effective or super effective on them. I had to cut that to deliver the game on time. But maybe I'll keep working on it and make a post jam version.