As other people have mentioned, there is a dance battle type situation in the later waves (started at around wave 20 for me).
At around wave 30 on king mode, the units started taking damage during the dance battle.
At wave 43, some of my units died from this damage, this meant that the battle never actually started (I assume because the game was waiting for units to get to a spot, but they were already dead, so they could not.)
This forced me to stop playing the game, as I waited for >10 mins on max speed, and the battle did not start.
Also, the balancing seems way off imo; Farm + library seems to be the only strategy that works past a certain point.
This strategy allowed me to get 2 units of over 100 units, that had like 70 chain lightning and 60 armor perks (I forget what its called, but its the one that nullifies damage.)
Overall, I enjoyed the game, and am looking forward to future updates :)
- From a web-build player