I actually really wanted to enjoy this game, and I was way too addicted to it, but after playing for over three hours I had just reached 150 enemies killed for the very first time, and then I died instantly when the new type spawned. The enemies spawn too slow, attack instantly after spawning half the time, and do too much damage for not having any ability to heal.
Also, 50% of the upgrades literally felt useless. "Right now I can kill this enemy in 5 slashes, so let's upgrade Melee for all this ether I've built up with several runs, and now... I can kill this enemy in 5 slashes." I really started to think, did the developer even play their own game? Upgrades are supposed to make you stronger, you know? I upgraded Health 8 times - still die without even realizing I'm low. Upgraded Melee 6 times - still takes more than 3 hits to kill the most basic monster. This feels like an arcade game that wants me to keep giving it my money.
What I can say I loved is the concept on its own - I very much enjoyed killing the monsters and figuring out strategies, and all that was even more fun once I knew I could dash and walljump and being able to do those things is probably what kept me playing because I enjoyed them so much. So the conclusion is: Cheaper prices, stronger upgrades, more currency gained, or less enemies are all options that would make the game near-perfect. If there's a balanced-out sequel with at least one of these four things it could be a 10 or a 5 or whatever Newgrounds' top rating is!