I really enjoyed this game! It was fun, and feel very polished and well designed, so good job! Here's some of my thoughts:

What I liked:

• The mechanics are interesting and work really well together. I like that the slimes aren't just obstacles, there are cases where you can use them as tools to help solve the puzzle. Things like this keeps the game interesting.
• The art style is cute and fits the game well. The sprites are well done.
• I'm on level 19, and so far, the puzzles are well done overall. Few of them feel unfair, and most of them gave me that "Aha!" moment once I figured them out.

Suggestions/Small Critiques:

• In whichever level you first need to get rid of the slime with the spikes (I think it was 13), it took me forever to figure that out. Maybe it was just me (it seems obvious in retrospect), but I felt like there was no indication that that was even a possibility.
• Also around level 13/14, there was a huge difficulty spike, at least for me. I went from figuring most levels out in 2-3 tries, straight to it taking me a long time to figure each level out. I don't mind the harder levels, but it seemed kind of sudden. I know it's tough to balance, but a more gradual increase in difficulty would likely be better for most players, in my opinion.
• Occasionally, there's a glitch where after picking up a box, I couldn't move to where the box was. If you'd like I can try to figure out the levels where it happened.
• The character movement feels kind of slow to me, and it makes the whole game feel a little slow. Making the character just a little faster would make the game feel much smoother and snappy (again, in my opinion).
• The "Level Failed" screen also feels too long to me. I found myself rushing to click the restart button just to avoid having to sit through that screen for a few seconds. It wasn't horrible because I could press the restart buttons, but the few times I didn't get to it in time were annoying. Just making it slightly shorter or skipping it with a click would be great,
• The door sprites are a bit confusing. When they're blocking your path horizontally, it looks like you should be able to walk behind them. It's not really that bad, but I think something like a simple box/block with a lock on it would make more sense and look less confusing/jarring.
• This would make a great game for mobile! It would work fine with a simple "swipe in the direction you want the character to go" control. I don't know what engine you're using, but if it's something like Unity or Godot where porting it isn't a big deal, then i think adding touch controls would be worth it. I would gladly download this on my phone.

Sorry if this is too long, but I like to give detailed feedback. And don't take the long list of suggestions wrong, I really like the game!

Ultimately this is your game, and you have to decide what to put in it, so don't feel like you have to use even any of my suggestions. I look forward to seeing it improve and will definitely play it more!