Hello! Here is another update with few more improvements.
Changelog:
1) Walls rebalance:
Now walls cannot be destroyed by shadows, but still, shadow warriors will try to attack them (it works as some kind of distraction). Other shadow types can outflank walls as usually.
2) Added a hint when new enemy types going to appear in order to make it easier to prepare your defense in time.
3) Small bug fixes.
Thank you for your bug reports. Have a nice day!