This is cool! It took me a bit to figure out what was actually happening and get a handle on the controls, but once I did it was pretty fun (Very difficult, but fun lol).
As a few others have pointed out, I think having the game start out a bit easier, then ramp up would help with that initial confusion. Understanding the controls, dropping lily pads, and frog killers all out once is a lot. Maybe you could only spawn in the frog killers after a certain amount of time or flies caught? Then the player at least has a little bit of time before they have that pressure put on them.
Overall, great job!