Nice little game!
For the amount of games that deal with scaling objects to solve puzzles (mine included) I honestly felt as though this one was pretty creative, in which you place down where they are, and can get them back if you retract them back all the way. That allows for some pretty unique levels to be made, although I don't think you had any that required placing the same thing down multiple times.
You have a lot of potential for more puzzles to be made here, you got a few different mechanics in but only ended up using them once, like the white blobs or the one that changes in both directions. I can think of a few ideas that could be made with these already, and you still have room to explore into more objects and mechanics entirely. I would also like to see more levels that incorporate the ability to block other things from growing, since I think that is a relatively unique feature compared to other games within this jam.
But, I can see how the time constraints hinder the ability to create more levels, and you managed to introduce new concepts despite it. (Also camping during a game jam... thats probably a huge factor, although cool.)
The controls were a bit unintuitive, I didn't figure out that placing would always be below me until awhile, even if it may seem obvious. I prefer having number keys for selecting things, so providing options could be something you would look into.
I highly recommend having some form of menu for you game, to house basic things like options for sounds and skipping / viewing levels. It is a bit of chore work to set up, but they go a long way for the user experience, you always want players to keep playing your game, and weather that means they mute the volume or be able to skip a level when stuck, you give them the tools to do so.
The visuals were very nice though, there was a lot of juice for such simplistic movements.
Good work!