I have no idea if I'm wrong, or if the game's wrong, but something's screwy.
I managed to luck out early by upgrading my "Ero-Cannon" as quickly as possible, netting me massive heaps of experience. Everything seems to go just fine—damage upgrades, speed boosts, magnetic field increases. The Growth stat doesn't feel like it does much of anything...
...but worst is when I start taking the other bonuses. I take a Health power-up at one level, and instead of "increasing my HP by 30%" or whatever, it cuts my total HP to 30%. Likewise, I take an EXP Gain power-up in another run (because obviously I died in the first one where I took the Health power-up), and at Level 40, I went from flying through levels to getting nothing from either the silver or gold EXP gears; progress stalls, I get inundated by the strongest enemies moving as fast as I move from all sides, and inevitably die... again... and again... and again. So it seems that at Level 40, the amount of EXP needed to gain a level just shoots up into the stratosphere, and is not a function of whether or not you have a busted EXP Gain power-up. That's on me for not knowing.
Having both touch and WASD controls at the same time can cause some pretty big errors in playing, as just one errant click could send you careening into a horde of chasing enemies. And I see a "Sync" bar on the side, but I have no idea what it does, how I'm supposed to increase it, or even if I can.