Great take on the theme! I appreciate that it's not just "you play as the enemy" but rather has you swapping back and forth between defense and attack. It really sets it apart from other submissions.
When it comes to critiques, the other reviews have covered the feedback well. I can agree that if development were to continue that the "attack" phase needs the most work. With more unique unit movement patterns, some general polishing, and maybe even a story this could truly become a unique product.
Overall great work! You've come up with a very expandable and versatile project idea and I think it has great potential to be taken further!