I did initially plan to include one (that fourth screenshot), but I soon learned bosses are quite challenging to design since you can't just create behavior and drop them in a level - you actually have to create an entire puzzle and sequence of events around them within a specific space, so it was much harder to squeeze into the final month of development.
Unfortunately, I don't think I can really afford to work on a game that isn't helping to pay my bills, so it actually might be a while before there is any meaningful update like a boss. Therefore, a boss might not be the next thing I focus on - as it might be more efficient to work on other features that are smaller in scope so that I can accomplish more within a specific period of time. I'll have to think about what's next on the agenda when time permits.