Collision detection (kinda)

for _, entity in pairs(Isaac.GetRoomEntities()) do  -- go through every entity in the room
       if entity.Type ==
       and entity.Variant ==  then -- look for your shield entity
           local shield = entity
           -- you found your shield entity
           for _, entities in pairs(Isaac.GetRoomEntities()) do  -- go through every entity in the room again
               if entities.Type == EntityType.ENTITY_PROJECTILE then -- look for enemy projectile.
                   local shot = entities
                   -- check collision
                   if (shot.Position - shield.Position):Length() <= shot.Size + shield.Size then
                       -- remove projetile if it is one the same position than the shield
                       shot:Remove()
                   end
               end
           end
        end
    end
end