In advance, please don't see this as an attack against you or your game; it is feedback. I quite enjoyed some of the levels, and there was certainly moments of intense action, managing resources, balls and powerups. The achievements were a very cool touch, and the menus were clearly a heavy focus, which really improved the experience.
Neat that you implemented a friend system, but it seemed a bit pointless... I couldn't challenge friends or easily see their scores. It also required me to put in a username and password. No offense, but I put in a fudge password (can never be too sure with third parties) that I already forget, so I feel that the friend system is more detrimental to the game than useful. I really don't see the need for an online feature, particularly if the game doesn't rely on it. Maybe accounts could be optional? Or perhaps offer some form of gamemode that utilises online features, like a 1v1 vs? Maybe a challenge mode where each friend completes a level and is ranked on performance?
There was also a lot of stuff that I didn't get. I didn't understand that the particles were currency, and was confused as to how the points went up. I also thought that the ball direction was randomised on hit, but after a while of playing, I realised that the direction depended on where you hit the ball. When initially writing this feedback I thought the leaderboard was busted, but no, you needed to click another button. This feels weird, particularly since there is only one leaderboard.
Overall, the gameplay was fun, but the currency system was a bit of a bummer. Having to purchase extra levels feels counter-intuitive, particularly since you earn less than you pay to purchase the level (resulting in an overall loss). There didn't seem to be a way to lose either, since negative points was a thing. It was quite fun when I had ten+ balls on the screen, but the game didn't reward me for doing this, as the balls were quickly lost and didn't earn back the 500+ points used to purchase them. This resulted in the best strategy being a single ball, which was incedibly slow.
Honestly though, the game was quite fun, but it took a bit of learning before actually being any good. For the first few games, I was frequently in deficit, rocking a (solid) negative score. Once learnt though, I was able to rack up some decent scores, and you'll even find me on the leaderboard (assuming I haven't been overthrown). Will be sure to check out your other stuff!