Nice! I got to level 21 before a single enemy slipped through. Lost in 22, got totally stomped. Not sure what I could have done differently. Maybe the game could need more indicators like range and cooldown to make it more transparent what went wrong. Maybe cast time was an issue with such fast enemies?
Viewing post in Remnants of the Past : Defend Neuro's Memories comments
Yes, the game starts to become challenging starting wave 21.
For a range indication, you can hover your mouse over the "Upgrade Range" button.
Not sure what you mean by cooldown, the Atk/s indicates how many attacks per second a unit does.
Protip on how to deal with fast enemies starting at wave 21, the drones have homing missiles, so they cannot miss.