Yeah, I definitely understand what you mean by the latter end of the game being a bit more rough. While most of my favorite puzzles in the level are there, the pacing isn't always as stellar, which is especially because that 40-50 segment you mentioned was intended to be the most smoothly-paced part of the game. I feel like part of this is due to the inherent complexity of the concepts at that point making for especially tough platforming, but another part of it is KS itself clearly buckling under the weight of said complexity. Screens are static and small, and in order to stuff in a concept that requires so much room to function properly, I ended up having to really pack in certain things, and this shows with the awkward difficulty curve of some of those screens.
Nonetheless, I feel did the very best I could ensuring that stretch of gameplay was at least fairly enjoyable; I'd received a massive chunk of heart-breaking feedback from the first playtester to complete it, so I'm glad I went through, smoothed out the bumps, and then repeated the process with another tester. It's clear that more could have been done, but my exhaustion with Deep Freeze, confusion as to how to further adjust difficult, and desire to stop sitting on it for so long, led me to release it in this state, which I'm ultimately satisfied with.
(Sergio also mentioned feeling that the bit at the very end should have been a little longer. In retrospect, I totally agree, but I couldn't come up with any particularly enticing ways to expand on the idea, and I was concerned that players might find it more annoying than interesting. If nothing else, I've at least left the door open for someone else to expand on that one.)
I don't disagree that more story may have benefited the level, but I can't shake the feeling that it would have severely extended development time and may have made it difficult for me to make some of the free-form changes that I was always making to the level design. In the future, I'd definitely like to construct a more visually and narratively* complex experience, but my goal with Deep Freeze was simply to make something big, and something fun, and I knew that simplicity would be the ideal way to keep me moving forward.
The cyan artifacts were intended to give more experienced KS players something more interesting to focus on in the early part of the game. Much like the story, the use of the cyan artifacts was something that succumbed to me just wanting to get the level done. The red ones do serve a purpose, but it's very, very niche, and requires one to find a bizarrely-hidden secret.
Anyhoo. I'm glad you enjoyed the level, and I strongly appreciate the sentiment that you'd be willing to pay money for even just some part of it. It's a motivating thought, even if I have no intention of releasing anything commercially for quite some time.
*Apparently not a word