Welp. Not terribly original, HOWEVER, it was a metroidvania and I am impressed by how fancy you did all this in a few hours. I wish you had went ahead and actually finished the overworld like you wanted to, as the ending was... anticlimactic. In fact, there wasn't an ending at all.
I loved the music, I loved the art, and the programming, though a little glitchy, wasn't half bad.
Here are some tips for the next time around:
Block shoving needs to be faster UNLESS it's an element of a puzzle. Which it never was.
You seemed to like shoving water where it was not needed, do you really have to put water in the puzzle with the four blocks?
The stair part was just frustrating. Put a platform or two eventually so you don't have to start all the way over, ya know? That was like a 1/3 of my game right there.
Maps. If you're gonna do a metroidvania, you gotta have a map. Give a general sense of where you've been, you don't have to go metroid style and say where the doors are.
After you get the climb and jump, I love how you let people roam completely free. Do that more often. However, it helps to have three real 'layers.'
No power layer, some power layer, then the 'last power' layer. Maybe have it more lush.
Now the glitch zone was... uncessary. What the heck was that anyways? At least it was a change of pace I spose, if you were TRYING to build a story with the weird blackhole spots and the glitch zone, in blew right past me. I know you had no time, but if you want to put in some backstory you might wanna put some ruins or something, maybe even incorporate them into the puzzle. Remember, this is IF and ONLY IF you want that to be a thing.