Was catching flies ever meant to be fun?
Just overall a boring game.
Pointing at flies to see if you can catch 25 within a timeframe of a minute doesn't seem like the greatest concept for fun and turns out that it isn't.
First of all just pointing at time even isn't that engaging considering that you have to keep the mouse over the flies for at least a couple of seconds takes up to much time for the time limit to be viable. I also found that even if the square was on a fly if it missed by a tiny bit it wouldn't catch it along with even if its perfect that it sometimes wouldn't count so your hit detection is off as well. Overall this problem could be solved with having clicking control the time the tongue goes to catch a fly instead of a time delay, it'd make the task easier and probably more fun.
Now presentation was subpar for both graphics and sound. Just the sound effects of the flies get annoying in under 30 seconds, at least for me it did, with no music in game to at least cover up some of it. This basically just makes it so the player will get more annoyed by just even the sound. The music you do have in the game is your generic looping soundtrack and just ended up becoming another annoyance, try to get/come up with something at least tolerable if possible. Graphics wise the drawings just really need to be improved in both shape and detail, but basically it really is just the detail of it that needs to be improved. Now I'm not against generic looking flies but just at least try to make them look more then just black circles with red things for eyes. Basically though it just comes down to just improving yourself as an artist overall for this part.
Hopefully your next attempt will be better, at least concept wise. Oh and also check your spelling next time.