= els.answer.value.trim();
        if (raw === '') {
          blink(els.answer);
          return;
        }
        const guess = Number(raw);
        const correct = Number(state.current.ans);
        if (Number.isFinite(guess) && guess === correct) {
          state.correct += 1;
          state.attempts += 1;
          state.streak += 1;
          if (state.streak > state.bestStreak) state.bestStreak = state.streak;
          feedback('Correct!', true);
          updateStatsUI();
          nextProblem(