First, the player reaches level 40, and then gets an upgrade after completing the specified goal in the game. It is still a bit difficult to prompt the upgrade requirements in the specific game.
Every player should have encountered such a thing in his game career: when playing a game, he never used some small skills built into the game, and even didn't notice the existence of the core system. Until he saw the discussion of these small skills by netizens, he was shocked and shouted.