Design wise, I thought it was pretty good. The levels are really thought out, and I can tell you spent a lot of time planning it all, and the art is great. That being said, development wise - it needs a ton of work. There are a lot of bugs, the controls are a bit weird, and the fact that the only audio is when you click restart was an odd choice (I would have made the jump sfx before any other sounds). As far as the bugs, as I said there were a lot. The first one is that at the first door, if you walk against the wall you will fall endlessly through the ground (see attached screenshot). There were several strange collider issues like this throughout the game. The second bug I encountered was if you fail to jump over the green (thingy?) in the first room to push it to the left and accidentally push it against the other one next to it, they both get stuck and you can't push them anywhere. Next, I was in the room after the statues that shoot the red flames - I walked into a door that led to a blue area (which was a really cool, upside down room - again the design is great, just the execution needs work), but there was nowhere to go, and I couldn't go back through the door. I noticed that pushing E in that room placed a permanent big blue crystal over the player's head, but beyond that none of the controls did anything, and restarting just restarted that room. I found myself having to refresh the browser multiple times in order to force a restart when bugs happened.
Having said all that, I think your design skills are excellent. They just seem to outweigh your other skills by quite a bit. I suggest the next jam you do, to join a team where you are the lead designer. It's clearly where you shine. I loved the level design, the puzzles, the art, the transitions between scenes, basically every aspect of the design side of the game was superb, so great job on that! Anyway, here's the image I mentioned above:
