Wow! I really like this! I haven't played it but I looked in LM (I was expecting a puzzle similar to Shell Puzzle, which is too hard to do blind), and it looks quite good!
Some minor points are that you use the Yoshi+Shell glitch, as well as block factory, If you use those players might start to abuse those more often thinking that it's intended, so you have to be really careful with your level design once you implement these glitches.
Also duckjumping is not fun.
Other than that it looks good, make sure to watch out with those glitches!
--------------------Of course you should fight fire with fire, you should fight everything with fire.
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Sadistic Designer - testing Pit without tools.