The levels are greatly designed but, some things have been downgraded from the original. Most notably, 3-5.
The Bomb mechanic was really interesting in the original and stripping it here wasn't the best decision. Its became a really dull level.
3-6s first area could use better music, either a sampled version of the one used or a completely new song.
Even though 3-Castle royally sucked, it lost a bit of it's identity by removing the toxic rising section. Maybe add a toxic rising section but either make the toxic rise slower or make the section shorter.
I also collected a broken star coin in 3-3, this also occurred in 3-5 with the second star coin but I didn't get to screenshot it.
Lots of love and good luck on the project wishes, S1Z2