Thank you for the kind words!
Yeah, Level 11 was meant as the chapter's ultimate test, which explains why it's so difficult. It was meant to be the final level of the chapter.
I'm sort of hesitant about adding obstacles in Level 7 because of the unusual nature of the stage and I don't want to make it too complicated again. In the initial stages of the level, the final section involved a rocket launcher, but it made the section a bit too frustrating. While the initial design definitely belonged in the mid-section of the chapter, it now fits pretty well as an early level in the chapter and the chapter do require a few easier stages.
Thanks for the comment about Level 3, this was one of my personal favorites from this chapter in overall. I wanted to add a new twist to backtracking while not making it blatant or anything.
Level 12 had the top path easier in design in order to clearly differentiate both paths. The top path involves precision and patience, the second one favors twitch reactions. Also, the top path is easier because it doesn't hand any reward to the player. The other path allow the player to get the bandage as it's harder.
As for me completing the chapter, it's already finished and all of the levels have finally been uploaded on the portal. I just waited to finally have the thing compiled in the chapter creator to make it "official" before I'd post the other levels, but it's been delayed as I'm unable to get the chapter creator to work on my computer, so the full chapter and its difficulty curve can't be uploaded for the time being. I might as well announce the other levels now since I'm replying to this thread.
Level 18 - Aerobatics
Crazy jumping ahead! You have to jump onto the gravity wells in the first section to avoid the rocket launchers as you're being whisked up and down. The other section features a less frantic pace but yet another pesky gravity well to deal with.
Level 19 - Infinity Cubed
A patience level, or "how much gameplay can one cram in a 24x20 level". A lot of the corners have those four-way turrets, but they all fire slowly and in unison. They mainly represent a threat when they fire in straight lines or when you're close to them when they shoot. The level opens itself more and more as you progress. It shouldn't be too hard if you take it slow.
Level 20 - Mausoleum
An attempt at a more atmospheric looking map. It's broken up in clear sections that all have their own hazards. The fly isn't a problem until you get to the final tower climb... if you're fast enough. Loafers are not tolerated here!