/* A simple CSS reset and typography for a clean start */
        :root {
            --light-bg: #F5F5F7;
            --white-bg: #FFFFFF;
            --text-dark: #1D1D1F;
            --text-gray: #6E6E73;
            --primary-blue: #007AFF;
            --red: #FF3B30;
            --yellow: #FF9500;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Inter', sans-serif;
            transition: all 0.3s ease;
        }

        body {
            background-color: var(--light-bg);
            color: var(--text-dark);
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        /* Responsive Navigation Bar */
        .navbar {
            width: 100%;
            background-color: var(--white-bg);
            padding: 1rem 2rem;
            box-shadow: 0 1px 3px rgba(0, 0, 0, 0.08);
            display: flex;
            justify-content: center;
            align-items: center;
            position: sticky;
            top: 0;
            z-index: 1000;
        }

        .nav-links {
            display: flex;
            list-style: none;
        }

        .nav-link a {
            text-decoration: none;
            color: var(--text-gray);
            font-weight: 500;
            padding: 0.5rem 1rem;
            border-radius: 8px;
            transition: color 0.3s, background-color 0.3s;
        }

        .nav-link a:hover,
        .nav-link a.active {
            color: var(--text-dark);
            background-color: rgba(0, 0, 0, 0.05);
        }

        /* Main Content Container */
        .container {
            flex: 1;
            width: 100%;
            max-width: 900px;
            padding: 2rem;
            display: flex;
            justify-content: center;
            align-items: center;
        }

        .content {
            width: 100%;
            background-color: var(--white-bg);
            border-radius: 20px;
            box-shadow: 0 10px 30px rgba(0, 0, 0, 0.05);
            padding: 3rem;
            text-align: center;
            opacity: 0;
            transform: translateY(20px);
            animation: fadeIn 0.5s forwards;
        }

        /* Stopwatch Styles */
        .stopwatch-container {
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        .timerDisplay {
            font-size: 3rem;
            font-weight: 700;
            display: flex;
            align-items: center;
            justify-content: center;
            gap: 0.5rem;
            flex-wrap: wrap;
        }
        
        .time-part {
            display: flex;
            flex-direction: column;
            align-items: center;
        }

        .time-value {
            font-size: 3rem;
            font-weight: 700;
            color: var(--text-dark);
        }
        
        .time-label {
            font-size: 0.8rem;
            font-weight: 500;
            color: var(--text-gray);
            text-transform: uppercase;
            letter-spacing: 0.05rem;
        }

        .separator {
            font-size: 3rem;
            color: var(--text-gray);
        }

        .buttons {
            display: flex;
            gap: 1rem;
            margin-top: 2rem;
        }

        .btn {
            font-size: 1rem;
            padding: 0.75rem 1.5rem;
            border-radius: 10px;
            border: none;
            font-weight: 600;
            cursor: pointer;
            transition: transform 0.2s, box-shadow 0.2s;
        }

        .start-btn {
            background-color: var(--primary-blue);
            color: var(--white-bg);
        }
        
        .stop-btn {
            background-color: var(--red);
            color: var(--white-bg);
        }

        .reset-btn {
            background-color: var(--yellow);
            color: var(--white-bg);
        }

        .btn:hover {
            transform: translateY(-2px);
            box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
        }

        /* About Page Styles */
        .about-page h1 {
            font-size: 2.5rem;
            margin-bottom: 1rem;
            color: var(--text-dark);
        }

        .about-page p {
            font-size: 1rem;
            line-height: 1.6;
            color: var(--text-gray);
            margin-bottom: 1rem;
        }

        /* Animations */
        @keyframes fadeIn {
            to {
                opacity: 1;
                transform: translateY(0);
            }
        }
        
        /* Mobile Responsiveness */
        @media (max-width: 768px) {
            .navbar {
                padding: 1rem;
            }

            .nav-link a {
                padding: 0.5rem 0.75rem;
            }

            .content {
                padding: 2rem 1.5rem;
            }

            .timerDisplay {
                font-size: 2rem;
                flex-direction: column;
            }
            
            .time-value {
                font-size: 2rem;
            }

            .separator {
                font-size: 2rem;
                margin-top: -0.5rem;
            }
            
            .buttons {
                flex-direction: column;
            }
            
            .btn {
                width: 100%;
            }
        }