SUPER awesome! Very challenging levels, awesome art style, and were those Undertale sound effects thrown into the mix?
Sometimes if I died and I was holding left/backward for whatever movement I needed, I often ended up drifting back into the previous level on accident, which I had some concerns over since I was afraid of accidentally dying in that previous level and having to start from there again. I don't know if preventing you from going back to a previous level would be too much handholding for this type of game, though, so it's not that big of a gripe for me. Overall, fantastic job!