/* 헤더 네비게이션 */
        header {
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            padding: 25px 60px;
            background: rgba(0, 0, 0, 0.3);
            backdrop-filter: blur(30px) saturate(200%);
            border-bottom: 1px solid rgba(255, 255, 255, 0.05);
            z-index: 1000;
            transition: all 0.5s cubic-bezier(0.22, 1, 0.36, 1);
        }
        
        header.scrolled {
            padding: 18px 60px;
            background: rgba(0, 0, 0, 0.72);
            backdrop-filter: blur(24px) saturate(180%);
            border-bottom-color: rgba(255, 255, 255, 0.08);
            /* 미니멀 분리: 콘텐츠 위 가독성 해치지 않는 얇은 hairline + 소프트 드롭 */
            box-shadow:
                0 1px 0 rgba(255, 255, 255, 0.04),
                0 4px 16px rgba(0, 0, 0, 0.12);
        }
        
        nav {
            display: flex;
            justify-content: space-between;
            align-items: center;
            max-width: 1600px;
            margin: 0 auto;
        }
        
        .logo {
            font-size: 2rem;
            font-weight: 900;
            background: linear-gradient(135deg, #5b4cff 0%, #00d4ff 100%);
            -webkit-background-clip: text;
            background-clip: text;
            -webkit-text-fill-color: transparent;
            text-decoration: none;
            letter-spacing: -0.02em;
            position: relative;
            transition: all 0.3s ease;
        }
        
        .logo::after {
            content: '';
            position: absolute;
            bottom: -5px;
            left: 0;
            width: 0;
            height: 3px;
            background: linear-gradient(90deg, #5b4cff 0%, #00d4ff 100%);
            transition: width 0.3s ease;
        }
        
        .logo:hover::after {
            width: 100%;
        }
        
        .nav-menu {
            display: flex;
            gap: 50px;
            list-style: none;
            align-items: center;
        }
        
        .nav-menu a {
            color: rgba(255, 255, 255, 0.7);
            text-decoration: none;
            font-weight: 500;
            font-size: 1rem;
            transition: all 0.3s ease;
            position: relative;
            padding: 5px 0;
        }
        
        .nav-menu a::before {
            content: '';
            position: absolute;
            bottom: -2px;
            left: 0;
            width: 0;
            height: 2px;
            background: linear-gradient(90deg, transparent, #5b4cff, #00d4ff, transparent);
            transition: width 0.3s ease;
        }
        
        .nav-menu a:hover {
            color: #fff;
            text-shadow: 0 0 20px rgba(91, 76, 255, 0.5);
        }
        
        .nav-menu a:hover::before {
            width: 100%;
        }
        
        .nav-cta {
            padding: 14px 35px;
            background: linear-gradient(135deg, #5b4cff 0%, #00d4ff 100%);
            color: white;
            border: none;
            border-radius: 60px;
            font-weight: 700;
            font-size: 1rem;
            cursor: pointer;
            transition: all 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
            text-decoration: none;
            display: inline-block;
            position: relative;
            overflow: hidden;
            box-shadow: 0 5px 20px rgba(91, 76, 255, 0.3);
        }
        
        .nav-cta::before {
            content: '';
            position: absolute;
            top: 50%;
            left: 50%;
            width: 0;
            height: 0;
            background: radial-gradient(circle, rgba(255, 255, 255, 0.3) 0%, transparent 70%);
            transform: translate(-50%, -50%);
            transition: width 0.6s ease, height 0.6s ease;
        }
        
        .nav-cta:hover::before {
            width: 300px;
            height: 300px;
        }
        
        .nav-cta:hover {
            transform: translateY(-3px) scale(1.05);
            box-shadow: 0 15px 40px rgba(91, 76, 255, 0.5);
        }
        
        /* 모바일 메뉴 토글 */
        .menu-toggle {
            display: none;
            flex-direction: column;
            cursor: pointer;
            position: relative;
            width: 30px;
            height: 25px;
        }
        
        .menu-toggle span {
            width: 100%;
            height: 3px;
            background: linear-gradient(90deg, #5b4cff 0%, #00d4ff 100%);
            position: absolute;
            transition: all 0.3s ease;
            border-radius: 2px;
        }
        
        .menu-toggle span:nth-child(1) { top: 0; }
        .menu-toggle span:nth-child(2) { top: 50%; transform: translateY(-50%); }
        .menu-toggle span:nth-child(3) { bottom: 0; }
        
        .menu-toggle.active span:nth-child(1) {
            top: 50%;
            transform: translateY(-50%) rotate(45deg);
        }
        
        .menu-toggle.active span:nth-child(2) {
            opacity: 0;
        }
        
        .menu-toggle.active span:nth-child(3) {
            bottom: 50%;
            transform: translateY(50%) rotate(-45deg);
        }