Sooo, I've done 5 runs and completed only 1 one them which means it's doable. Hard, but doable. The waves are completely RNG based: sometimes the game keeps throwing 3 lines of enemies each waves and sometimes it just doesn't spawn them at all for 3 waves in a row. And I haven't completely figured it out whether certain enemies appear on certain locations or it's just a bad luck. Overall, the game has a great potential as well as it needs improvement. Hoping that it won't be abandoned :)