Liked the idea, but there are some things that frustrated me, so I'll try to give some constructive feedback if you wanna continue this project or expand the game :)
The colors yellow and blue didn't ring any bell to me, didn't tap on any common knowledge that would help me learn which of them make large or tiny, so I kept using the wrong projectile, shrinking when I wanted to scale and vice-versa. I think green to grow and red to shrink would make it easier to learn and the game more readable. Green is commonly 'good' in games, and 'red' bad, so good to grow and bad to shrink I think would make more intuitive. But ideally, the guns could have different shaped guns and projectiles, like a "+" and a "-" for projectiles and like a big crossbow for "+" e a tiny laser gun for "-", this would help a lot too.
On the first level with a box, there were no clues that the box would also be affected by the projectiles, so I kept trying to stack the two boxes on the starting size, and it was really janky. Got so frustrated I almost quit haha but I ended up completing that level stacking the box, to later learn that the box could also scale and shrink. The physics with the boxes are a bit janky. The box slides and it always moved more than I intended to move them, and many times I had to reset the level for tiny mistakes that I didn't feel was my fault.
I did not finish the game as I ended up a bit frustrated, sorry. Maybe I'll try again later
Despite these details, I think the game is cool, there are some cool puzzles with these mechanics. Solid game, great entry and congratulations!