After the game begins, it's the player's turn, so you can click an action button(Items button doesn't work). You should also customize the shadow's attack and defense stats to tailor the battle how you want, or just click "Randomize Enemy Stats."
WORK IN PROGRESS: When it's done, it'll actually work properly. I wanted to recreate the battle system from a Persona game(mainly taking inspiration from P3/P4), and the User Interface was (obviously, to anyone who's played it) inspired by Persona 5. Everything was made from Scratch, in Scratch, by me. Except the costumes. Those are Scratch's.