I’ve gotten as far as adding the spawning mechanic. Here is a demonstration:
I also demonstrate the ability to move around and zoom the grid. This will allow more versatility and bigger levels, without making the squares unusably small.
The colours and icons are subject to change, although I quite like the monochrome filled in style. The list on the left and “Start battle” button are currently in Godot’s default style and font. I’ll definitely change those in the future. Currently the button doesn’t do anything except remove the spawn points from behind the programs.