Almost every action game needs the same thing: something that deals damage, and

something that takes it. In Godot 4 the raw tools are Area2D + CollisionShape2D,

but wiring them into a real hit is where people get stuck — collision layers vs

masks, stopping the player from hurting itself, not draining a target every physics

frame, and adding knockback and invincibility. Here's the whole thing, cleanly.