      timeLeft: parseInt(els.duration.value, 10),
          timerId: null,
          correct: 0,
          attempts: 0,
          streak: 0,
          bestStreak: 0,
          skips: 0,
          startTs: 0,
          current: null,
        };
      }

      function getSelectedOps() {
        const selected = [];
        for (const key of Object.keys(els.ops)) {
          if (els.ops[key].checked) selected.push(key);
        }
        return selected.length ? selected : ['add'];
      }

      function sum