Hey, just a stranger :)
I'm loving the introduction of core mechanics early on in your game as you expand into new enemy types. The notebook is a cute addition and reminds me of an RPG-lite inventory, and aesthetically there's a clean and simple color theme that's easy for the eyes to get used to. I'm excited to see you develop the visual style of this game further! Overall, things are looking nice and intuitive gameplay-wise.
One thing that might be cool to add would be to have the same enemies experience different movement styles in different levels (i.e. the random spawning of spikes was really fun to see, especially when they were static in the beginning levels). This could easily extend to the stink bugs with perhaps an airburst of their own to counteract players' own pheromones. I might also suggest slightly nerfing the butterflies, especially for introducing new players to the mechanic.
Great job!