Played this for a couple of turns and was really fun! Good to know that you had fun building this and are excited for future projects:) I have played thronefall so I get what you have tried to do here and it feels really good as a reverse tower defense. Its a good take on the theme, to flip the genre, definitely thinking outside the box there!
The artstyle is simple but effective for this sort of game and the music works well with the gameplay and art, felt very cohesive. From a gameplay point of view i like how you can control one character and rest driven by AI (very similar to thronefall) However i felt that there could have been more decision making since that is generally what player of this genre are looking for. The AI works well, but i think the behaviour especially of the enemy AI can be more refined. Adding health bars was great idea. To improve the feel further, you can look to add some juicy sound effects and particle effects for the combat. That would really improve the fun element of the game without investing too much time! Health bars for towers would also look good.
I think what you have here is a really great baselilne for a tower defense (or reverse tower defense) game and hope that you keep working on the project to polish it post the jam! Well done on this :)