   state.timeTotal = parseInt(els.duration.value, 10);
        state.timeLeft = state.timeTotal;
        els.timeLeft.textContent = String(state.timeLeft);
        updateHighUI();
        els.endMessage.classList.add('hidden');
        els.feedback.textContent = '';
        els.feedback.className = 'feedback';
        resetUIStats();
        setRunning(true);
        state.current = generateProblem();
        els.question.textContent = state.current.text;
        problemToFocus();
        state.startTs = Da