text: class User {
      constructor(username) {
          this.username = username;
          this.current_score = 0;
          this.id = '';
      }
  
      set gameDifficulty(level) {
          this.difficulty = level;
      }
  
      get gameDifficulty() {
          return this.difficulty;
      }
  
      static renderLogin() {
          const game_window = document.getElementById('game-window');
          // Create submission form with text input field and submit button
          const form = document.createElement("form");
          form.setAttribute('id', 'user-login');
          const input = document.createElement("input");
          input.setAttribute('type', 'text');
          input.setAttribute('id', 'user-input');
          input.setAttribute('placeholder', 'Enter Username');
          const submit_btn = document.createElement("button");
          submit_btn.setAttribute('id', 'user-submit');
          submit_btn.innerHTML = 'ENTER';
          
          // Add form to HTML document
          form.appendChild(input);
          form.appendChild(submit_btn);
          game_window.appendChild(form);
      }
  
      submitAndRenderScores() {
          const user = { u_name: this.username, u_score: this.current_score, u_diff: this.gameDifficulty };
          const configObj = {
              method: 'POST',
              headers: {
                  'Content-Type':'application/json',
                  'Accept':'application/json'
              },
              body: JSON.stringify(user)
          };
  
          fetch(USERS_URL, configObj)
              .then( response => response.json() )
              .then( function(user_obj) {
  
                  // After score submission to the database, the user's ID is retrieved and all of the user's scores are displayed
                  this.id = user_obj['data']['id'];
  
                  const scores_arr = user_obj['data']['attributes']['scores'];
                  const s_arr = [];
  
                  for(const elem of scores_arr) {
                      s_arr.push({'your scores': elem['score']});
                  }
  
                  const ordered_scores = s_arr.sort(function(a, b) {
                      return b['your scores'] - a['your scores'];
                  })
  
                  Game.renderScoreBoard(ordered_scores);
                  this.renderDeleteBtn();
          }.bind(this) );
      }
  
      renderDeleteBtn() {
          const game_window = document.getElementById('game-window');
          const delete_scores_btn = document.createElement("button");
          delete_scores_btn.innerHTML = "DELETE SCORES";
          delete_scores_btn.setAttribute('id', 'user-delete');
          delete_scores_btn.addEventListener('click', function() {
              if( confirm("Warning: Do you want to delete all of your scores? This action cannot be undone.") ) {
                  this.deleteScores();
              }
          }.bind(this));
              
          game_window.appendChild(delete_scores_btn);
      }
  
      deleteScores() {
          const user = { u_id: this.id };
          const configObj = {
              method: 'DELETE',
              headers: {
                  'Content-Type':'application/json',
                  'Accept':'application/json'
              },
              body: JSON.stringify(user)
          };
  
          const DELETE_URL = USERS_URL + `/${this.id}`
          fetch(DELETE_URL, configObj)
              .then( response => response.json() )
              .then( function(resp_obj) {
                  alert(resp_obj['Alert']);
                  window.location.reload();
          } );
      }
      
  }