A well-designed game core mechanic of a strategy defense game. Not intuitive as to what happens with your troops at first so adding a morale bar would help clear up the confusion. And also a health bar for enemies to turn on once they take damage.
Characters on screen compared to the overall screen size are small so adjusting their size could improve player’s focus on the gameplay. Along with adjusting the amount of unused screen space (skies) to further, improve the attention to the game.
Overall, an excellent thought out idea and implemented. The gameplay is fun and choice selection of order execution to obtain most cost-effective solution in game feels rewarding. Well done!