Source: models/keyboard.class.js

/**
 * Represents the state of the keyboard keys.
 * 
 */
class Keyboard {
   /**
    * Indicates if the left arrow key is pressed.
    * @type {boolean}
    * 
    */
   LEFT = false;

   /**
    * Indicates if the right arrow key is pressed.
    * @type {boolean}
    * 
    */
   RIGHT = false;

   /**
    * Indicates if the up arrow key is pressed.
    * @type {boolean}
    * 
    */
   UP = false;

   /**
    * Indicates if the down arrow key is pressed.
    * @type {boolean}
    * 
    */
   DOUWN = false; // Note: There is a typo here. It should be DOWN.

   /**
    * Indicates if the space bar is pressed.
    * @type {boolean}
    * 
    */
   SPACE = false;

   /**
    * Indicates if the 'D' key is pressed.
    * @type {boolean}
    * 
    */
   D = false;
}