Wearable device for using external entity as controller and method

A wearable device comprising:

• a display configured to allow external light toward a first surface to go through a second surface opposite to the first surface, and having a display area on the second surface;
• a memory for storing instructions;
• at least one camera;
• and
• at least one processor, the at least one processor configured to, when executing the instructions:
• display, via the display, content and a virtual object that is a GUI (Graphical User Interface) that controls a volume of the content,
• detect, via the at least one camera, a plurality of external objects,
• determine a shape matching one of the plurality of external objects among a plurality of designated shapes as a first shape of the one of the plurality of external objects,
• determine a type of input corresponding to the first shape and for controlling the volume of the content,
• based on the type of the input, detect, via the at least one camera, a user input for rotating the one of the plurality of external objects included in the type of the input for controlling the volume of the content, and
• based on the user input, control the virtual object displayed in the display.