:root {
            /* Light mode colors */
            --bg-primary: linear-gradient(135deg, #ffecd2 0%, #fcb69f 50%, #ff9a9e 100%);
            --bg-secondary: rgba(255, 255, 255, 0.95);
            --text-primary: #2d3748;
            --text-secondary: #4a5568;
            --text-muted: #718096;
            --border-color: #e2e8f0;
            --shadow: rgba(0, 0, 0, 0.1);
            --accent: linear-gradient(135deg, #4299e1, #667eea);
            --success: #48bb78;
            --danger: #f56565;
            --warning: #ed8936;
            
            /* Dark mode colors */
            --dark-bg-primary: linear-gradient(135deg, #1a202c 0%, #2d3748 50%, #4a5568 100%);
            --dark-bg-secondary: rgba(45, 55, 72, 0.95);
            --dark-text-primary: #f7fafc;
            --dark-text-secondary: #e2e8f0;
            --dark-text-muted: #a0aec0;
            --dark-border-color: #4a5568;
            --dark-shadow: rgba(0, 0, 0, 0.3);
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
            background: var(--bg-primary);
            min-height: 100vh;
            color: var(--text-primary);
            transition: all 0.3s ease;
            line-height: 1.6;
        }

        body.dark {
            background: var(--dark-bg-primary);
            color: var(--dark-text-primary);
        }

        /* Navigation */
        .navbar {
            background: var(--bg-secondary);
            backdrop-filter: blur(20px);
            box-shadow: 0 2px 20px var(--shadow);
            padding: 1rem 0;
            position: sticky;
            top: 0;
            z-index: 100;
            border-bottom: 1px solid var(--border-color);
        }

        .dark .navbar {
            background: var(--dark-bg-secondary);
            border-bottom-color: var(--dark-border-color);
        }

        .nav-container {
            max-width: 1200px;
            margin: 0 auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 0 2rem;
        }

        .logo {
            font-size: 1.8rem;
            font-weight: bold;
            color: var(--text-primary);
            text-decoration: none;
            display: flex;
            align-items: center;
            gap: 0.5rem;
        }

        .dark .logo {
            color: var(--dark-text-primary);
        }

        .nav-menu {
            display: flex;
            gap: 2rem;
            list-style: none;
            align-items: center;
        }

        .nav-item {
            position: relative;
        }

        .nav-link {
            color: var(--text-secondary);
            text-decoration: none;
            padding: 0.5rem 1rem;
            border-radius: 8px;
            transition: all 0.3s;
            font-weight: 500;
            cursor: pointer;
            display: flex;
            align-items: center;
            gap: 0.3rem;
        }

        .nav-link:hover {
            color: var(--text-primary);
            background: rgba(66, 153, 225, 0.1);
        }

        .dark .nav-link {
            color: var(--dark-text-secondary);
        }

        .dark .nav-link:hover {
            color: var(--dark-text-primary);
        }

        .dropdown {
            position: absolute;
            top: 100%;
            left: 0;
            background: var(--bg-secondary);
            min-width: 200px;
            box-shadow: 0 8px 25px var(--shadow);
            border-radius: 12px;
            padding: 0.5rem 0;
            opacity: 0;
            visibility: hidden;
            transform: translateY(-10px);
            transition: all 0.3s;
            border: 1px solid var(--border-color);
        }

        .dark .dropdown {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
        }

        .nav-item:hover .dropdown {
            opacity: 1;
            visibility: visible;
            transform: translateY(0);
        }

        .dropdown-item {
            padding: 0.75rem 1.5rem;
            color: var(--text-secondary);
            text-decoration: none;
            display: block;
            transition: all 0.3s;
        }

        .dropdown-item:hover {
            background: rgba(66, 153, 225, 0.1);
            color: var(--text-primary);
        }

        .dark .dropdown-item {
            color: var(--dark-text-secondary);
        }

        .dark .dropdown-item:hover {
            color: var(--dark-text-primary);
        }

        .theme-toggle {
            background: var(--accent);
            border: none;
            padding: 0.5rem;
            border-radius: 50%;
            color: white;
            cursor: pointer;
            font-size: 1.2rem;
            width: 40px;
            height: 40px;
            display: flex;
            align-items: center;
            justify-content: center;
            transition: all 0.3s;
        }

        .theme-toggle:hover {
            transform: scale(1.1);
        }

        /* Mobile menu */
        .mobile-menu-toggle {
            display: none;
            background: none;
            border: none;
            font-size: 1.5rem;
            color: var(--text-primary);
            cursor: pointer;
        }

        .dark .mobile-menu-toggle {
            color: var(--dark-text-primary);
        }

        /* Main content */
        .main-content {
            max-width: 1200px;
            margin: 0 auto;
            padding: 2rem;
        }

        .container {
            background: var(--bg-secondary);
            backdrop-filter: blur(10px);
            border-radius: 20px;
            padding: 40px;
            box-shadow: 0 20px 40px var(--shadow);
            text-align: center;
            max-width: 600px;
            width: 100%;
            margin: 0 auto 3rem;
            border: 1px solid var(--border-color);
        }

        .dark .container {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
        }

        h1 {
            color: var(--text-primary);
            margin-bottom: 10px;
            font-size: 2.5em;
            font-weight: 700;
        }

        .dark h1 {
            color: var(--dark-text-primary);
        }

        .subtitle {
            color: var(--text-muted);
            margin-bottom: 30px;
            font-size: 1.1em;
        }

        .dark .subtitle {
            color: var(--dark-text-muted);
        }

        .timer-circle {
            position: relative;
            width: 300px;
            height: 300px;
            margin: 30px auto;
        }

        .circle-bg {
            width: 100%;
            height: 100%;
            border-radius: 50%;
            background: conic-gradient(var(--border-color) 0deg, var(--border-color) 360deg);
            position: relative;
            display: flex;
            align-items: center;
            justify-content: center;
            box-shadow: inset 0 0 20px var(--shadow);
        }

        .dark .circle-bg {
            background: conic-gradient(var(--dark-border-color) 0deg, var(--dark-border-color) 360deg);
        }

        .circle-progress {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            border-radius: 50%;
            background: conic-gradient(#4299e1 0deg, #667eea 120deg, #764ba2 240deg, #4299e1 360deg);
            mask: radial-gradient(circle at center, transparent 120px, black 140px);
            -webkit-mask: radial-gradient(circle at center, transparent 120px, black 140px);
            transition: transform 0.1s ease;
            transform: rotate(-90deg);
        }

        .timer-display {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background: var(--bg-secondary);
            border-radius: 50%;
            width: 240px;
            height: 240px;
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            box-shadow: 0 10px 30px var(--shadow);
            border: 1px solid var(--border-color);
        }

        .dark .timer-display {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
        }

        .time-display {
            font-size: 3em;
            font-weight: bold;
            color: var(--text-primary);
            margin-bottom: 10px;
            font-family: 'Courier New', monospace;
        }

        .dark .time-display {
            color: var(--dark-text-primary);
        }

        .time-label {
            color: var(--text-muted);
            font-size: 1em;
            text-transform: uppercase;
            letter-spacing: 1px;
        }

        .dark .time-label {
            color: var(--dark-text-muted);
        }

        .controls {
            display: flex;
            gap: 15px;
            justify-content: center;
            flex-wrap: wrap;
            margin-top: 30px;
        }

        .time-input {
            display: flex;
            gap: 10px;
            margin-bottom: 20px;
            justify-content: center;
            align-items: center;
            flex-wrap: wrap;
        }

        .input-group {
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 5px;
        }

        .input-group label {
            font-size: 0.9em;
            color: var(--text-secondary);
            font-weight: 600;
        }

        .dark .input-group label {
            color: var(--dark-text-secondary);
        }

        .input-group input {
            width: 60px;
            height: 45px;
            border: 2px solid var(--border-color);
            border-radius: 8px;
            text-align: center;
            font-size: 1.2em;
            font-weight: bold;
            outline: none;
            transition: border-color 0.3s;
            background: var(--bg-secondary);
            color: var(--text-primary);
        }

        .dark .input-group input {
            background: var(--dark-bg-secondary);
            color: var(--dark-text-primary);
            border-color: var(--dark-border-color);
        }

        .input-group input:focus {
            border-color: #4299e1;
            box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.1);
        }

        .btn {
            padding: 12px 24px;
            border: none;
            border-radius: 25px;
            font-size: 1em;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.3s;
            text-transform: uppercase;
            letter-spacing: 0.5px;
            min-width: 100px;
        }

        .btn-primary {
            background: var(--accent);
            color: white;
            box-shadow: 0 4px 15px rgba(66, 153, 225, 0.3);
        }

        .btn-primary:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(66, 153, 225, 0.4);
        }

        .btn-danger {
            background: linear-gradient(135deg, #f56565, #e53e3e);
            color: white;
            box-shadow: 0 4px 15px rgba(245, 101, 101, 0.3);
        }

        .btn-danger:hover {
            transform: translateY(-2px);
            box-shadow: 0 6px 20px rgba(245, 101, 101, 0.4);
        }

        .btn-secondary {
            background: var(--border-color);
            color: var(--text-secondary);
        }

        .dark .btn-secondary {
            background: var(--dark-border-color);
            color: var(--dark-text-secondary);
        }

        .btn-secondary:hover {
            background: #cbd5e0;
            transform: translateY(-1px);
        }

        .preset-timers {
            margin-top: 30px;
            padding-top: 20px;
            border-top: 1px solid var(--border-color);
        }

        .dark .preset-timers {
            border-top-color: var(--dark-border-color);
        }

        .preset-title {
            margin-bottom: 15px;
            color: var(--text-secondary);
            font-weight: 600;
        }

        .dark .preset-title {
            color: var(--dark-text-secondary);
        }

        .preset-buttons {
            display: flex;
            gap: 10px;
            justify-content: center;
            flex-wrap: wrap;
        }

        .btn-preset {
            padding: 8px 16px;
            background: var(--bg-secondary);
            border: 1px solid var(--border-color);
            border-radius: 15px;
            color: var(--text-secondary);
            cursor: pointer;
            transition: all 0.3s;
            font-size: 0.9em;
        }

        .dark .btn-preset {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
            color: var(--dark-text-secondary);
        }

        .btn-preset:hover {
            background: rgba(66, 153, 225, 0.1);
            border-color: #cbd5e0;
            transform: translateY(-1px);
            color: var(--text-primary);
        }

        .dark .btn-preset:hover {
            color: var(--dark-text-primary);
        }

        .finished {
            animation: pulse 1s infinite;
        }

        @keyframes pulse {
            0% { transform: scale(1); }
            50% { transform: scale(1.05); }
            100% { transform: scale(1); }
        }

        .notification {
            position: fixed;
            top: 20px;
            right: 20px;
            background: var(--success);
            color: white;
            padding: 15px 20px;
            border-radius: 10px;
            box-shadow: 0 4px 15px rgba(72, 187, 120, 0.3);
            z-index: 1000;
            transform: translateX(300px);
            transition: transform 0.3s;
        }

        .notification.show {
            transform: translateX(0);
        }

        /* Instructions Section */
        .instructions {
            background: var(--bg-secondary);
            border-radius: 15px;
            padding: 2rem;
            margin: 2rem auto;
            box-shadow: 0 10px 30px var(--shadow);
            border: 1px solid var(--border-color);
        }

        .dark .instructions {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
        }

        .instructions h2 {
            color: var(--text-primary);
            margin-bottom: 1rem;
            font-size: 1.8rem;
            text-align: center;
        }
        

        .dark .instructions h2 {
            color: var(--dark-text-primary);
        }

        .instructions h3 {
            color: var(--text-secondary);
            margin: 1.5rem 0 1rem;
            font-size: 1.3rem;
        }
        .instructions ul li a{
            color: #8f99a8;
        }

        .dark .instructions h3 {
            color: var(--dark-text-secondary);
        }

        .instructions p, .instructions li {
            color: var(--text-muted);
            margin-bottom: 0.8rem;
        }

        .dark .instructions p, .dark .instructions li {
            color: var(--dark-text-muted);
        }

        .instructions ul {
            padding-left: 1.5rem;
        }

        .features-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 2rem;
            margin: 2rem 0;
        }

        .feature-card {
            background: var(--bg-secondary);
            padding: 1.5rem;
            border-radius: 12px;
            box-shadow: 0 5px 15px var(--shadow);
            border: 1px solid var(--border-color);
            text-align: center;
        }

        .dark .feature-card {
            background: var(--dark-bg-secondary);
            border-color: var(--dark-border-color);
        }

        .feature-icon {
            font-size: 2.5rem;
            margin-bottom: 1rem;
        }

        /* Footer */
        .footer {
            background: var(--bg-secondary);
            border-top: 1px solid var(--border-color);
            padding: 3rem 0 1rem;
            margin-top: 4rem;
        }

        .dark .footer {
            background: var(--dark-bg-secondary);
            border-top-color: var(--dark-border-color);
        }

        .footer-content {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 2rem;
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
            gap: 2rem;
        }

        .footer-section h3 {
            color: var(--text-primary);
            margin-bottom: 1rem;
        }

        .dark .footer-section h3 {
            color: var(--dark-text-primary);
        }

        .footer-section p, .footer-section a {
            color: var(--text-muted);
            text-decoration: none;
            line-height: 1.8;
        }

        .dark .footer-section p, .dark .footer-section a {
            color: var(--dark-text-muted);
        }

        .footer-section a:hover {
            color: var(--text-primary);
        }

        .dark .footer-section a:hover {
            color: var(--dark-text-primary);
        }

        .footer-bottom {
            text-align: center;
            padding-top: 2rem;
            border-top: 1px solid var(--border-color);
            color: var(--text-muted);
        }

        .dark .footer-bottom {
            border-top-color: var(--dark-border-color);
            color: var(--dark-text-muted);
        }

        @media (max-width: 768px) {
            .mobile-menu-toggle {
                display: block;
            }

            .nav-menu {
                display: none;
                position: absolute;
                top: 100%;
                left: 0;
                width: 100%;
                background: var(--bg-secondary);
                flex-direction: column;
                padding: 1rem 0;
                box-shadow: 0 5px 15px var(--shadow);
            }

            .dark .nav-menu {
                background: var(--dark-bg-secondary);
            }

            .nav-menu.show {
                display: flex;
            }

            .dropdown {
                position: static;
                opacity: 1;
                visibility: visible;
                transform: none;
                box-shadow: none;
                background: none;
                border: none;
            }

            .main-content {
                padding: 1rem;
            }

            .container {
                padding: 20px;
                width: 95%;
            }
            
            .timer-circle {
                width: 250px;
                height: 250px;
            }
            
            .timer-display {
                width: 190px;
                height: 190px;
            }
            
            .time-display {
                font-size: 2.2em;
            }
            
            h1 {
                font-size: 2em;
            }
            
            .controls {
                flex-direction: column;
                align-items: center;
            }

            .footer-content {
                grid-template-columns: 1fr;
                text-align: center;
            }
        }