Thanks so much; I'm glad you enjoyed it!
There are definitely jam limitations at play here (e.g. the character art, the soundtrack), and if I were to build this out further I very likely would explore additional movement and thematic abilities. The lock and key scheme I went with here is definitely scraping the floor of what can still be considered a Metroidvania, and while I'm generally happy with how the experiment played out, the sense of growing more and more capable and powerful over the course of the game … just doesn't land. For really large stages, I suspect that lack would be felt even more severely.
Still, if you haven't played around with the stage creation tools in the game, I do recommend giving them a try — it can be a lot of fun to explore what's really possible within the current set of constraints. :)