Age of war memories coming out haha
Good little game ! Fairly simple to understand and challenging.
Other people already mention the UI so I won't say it again.
For other things, maybe it would be fun to have a tree variation. Like if you focus on a tech to improve you could unlock new upgrades? (I know it takes time to do that haha).
Also I was wondering if it was not better to have your own spawns running until they meet a zombie, instead of stacking as a new wall.
Anyway well done :)