This was a really fun way to pass the time, but it was frustrating at times. The aiming is a little wonky, and sometimes the arrow would be beside the ball instead of in the center of it, which made it even worse. Admittedly, though, I should have been looking at the ball instead of the arrow more often, so it shouldn't have been as big of an issue as it was for me. I'm going to just attribute this to a skill issue, because the game was fun regardless and I suck so that would make sense.
Like a few other commenters, I found the upgrades to be a little lackluster. Although they were good and definitely helped, I was able to get all of them in the first five to ten levels. Granted, I replayed those levels over and over so that I could get A+ on all of them because the completionist in me couldn't stand it if I didn't, but I only replayed them a few times each, if that. The most I played any of the early levels was maybe three times. I feel like the upgrades should take a little more than that. I upgraded everything in order, and I was upgrading the purple goo before I even got to it in the game. At least put level restrictions on it or something so I can't upgrade it until I encounter it.
Honestly, though, the game isn't really about the upgrades, and it's still really fun. Even if getting an A+ on a few of the levels is basically entirely luck-based. Again, that's probably a skill issue and I'm being a petty sore loser. I did eventually get an A+ on all of them, though, if you're wondering. Very proud of myself, even if it's a pretty small accomplishment.
Also, I saw a few comments saying this game is too easy, which is weird. What did you expect? Pretty sure this game is made for children, bud. The challenge is supposed to be getting an A+ on every level, not, you know, just completing each level.