Very nice! The visual direction is great with the minimalism, but at first, I missed having some popups while hovering over the cards, to know what they do, as the icon are too symbolic and don’t indicate it too well. Also, some hit indications would be nice to know where the enemies hit the core radius, some particles or glowing stuff, just to know where to fortify the defences.
Really enjoyed taking care of the turrets, reminds me of playing Torbjorn in Overwatch. Good job!