This is a nice little one! Impressive what you can make in such a crunched down amount of time.
About what stuff you could add, I think it's just the controls that need a tiny bit more feedback. Everything being in one box at the top makes it hard to figure out what exactly I am doing, so maybe a different user interface would help.
Also, making it more interactive after you send out enemies could be interesting, like a bomb you send out and can press Space again to detonate it. It would make it more engaging after you validate each command?
Other than that, cooldowns and resource management are always fun design mechanisms to consider and work with.