This is a high-grade fountain pen design which has a shape gradually shrinks from the middle to both ends. When in use, the increase or decrease of the ink inside will cause the pen to fall toward the tip or the end, thereby implicitly prompting the user to refill the ink. When the ink is full, the center of gravity is shifted to the back so that the barrel is attached to the table and the tip is tilted. Conversely, when the ink is low, the end is tilted. This reminding method is both direct and inconspicuous, and can be smoothly conveyed to users in a form that people around will not notice.
