Very cool & juicy game ! Feels very addictive. it made me click rety a bunch of times :)
The visuals are cute. The sfx match neatly and pop nicely th music is really nice also and fit the game.
The difficulty are pretty well adjusted. (I would incease the easy mode sligtly as it tend to be very long before it ramps up)
I also agree with the feedback bellow. a rety button that make you jump right back into it is a big plus to keep you player engaged longer (the "okay one more try to beat that score" click is important for that kind of games)
In terms of improvement I don't see much. It's already pretty well rounded. Maybe add a more styled background. Maybe a few more kind of flies. Maybe a bonus fly that's harder to catch but give more points ?
Noticed a few grammar mistake, and the MC is stilled called a frog in the "how to play" section.
All in all It's a really cool mini game. would play really neatly on mobile. Great job :)