sentences:  There is also an on-screen gauge to display Star Energy, which is required to perform another type of move that accumulates in number as the player advances through the game.The player can locate hidden battle upgrades in the game's overworld, which promotes one partner character to a new rank at a time.Progression through "Paper Mario" depends upon interaction with the game's non-player characters (NPCs), who would often offer clues or detail the next event in the storyline.