/* 1. Root Variables & Reset */
:root {
    --primary-color: #6366f1;
    --secondary-color: #ec4899;
    --text-dark: #0f172a;
    --transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* 2. Cấu trúc Sticky Header */
.site-header {
    width: 100%;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    box-shadow: 0 2px 20px rgba(0,0,0,0.06);
    position: sticky; /* Hiệu ứng dính đầu trang */
    top: 0;
    z-index: 2000;
    transition: var(--transition);
}

.header-container {
    width: 100%;
    max-width: 1400px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 5%;
}

/* 3. Logo & Typography */
.logo {
    font-size: 24px;
    font-weight: 800;
    text-decoration: none;
    color: var(--text-dark);
    letter-spacing: -0.5px;
}

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

/* 4. Menu Styles */
.main-navigation .menu {
    display: flex !important;
    list-style: none;
    gap: 35px;
    margin: 0;
    padding: 0;
    align-items: center;
}

.main-navigation .menu a {
    text-decoration: none !important;
    color: var(--text-dark);
    font-weight: 700;
    font-size: 13px;
    letter-spacing: 0.5px;
    transition: var(--transition);
    position: relative;
}

/* Hiệu ứng gạch chân cho Trang chủ & Bài viết */
.main-navigation .menu a:not(.btn-contact-nav)::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    transition: var(--transition);
}

.main-navigation .menu a:not(.btn-contact-nav):hover::after {
    width: 100%;
}

/* 5. Nút LIÊN HỆ Đặc biệt (CTA) */
.btn-contact-nav {
    display: inline-block !important;
    background: #2f3542 !important; /* Màu nền tối gốc */
    color: #ffffff !important;
    padding: 10px 28px !important;
    border-radius: 50px !important;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1) !important;
    transition: var(--transition) !important;
}

/* Hiệu ứng Hover cho nút Liên hệ */
.btn-contact-nav:hover {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color)) !important;
    transform: translateY(-3px) scale(1.05);
    box-shadow: 0 8px 20px rgba(99, 102, 241, 0.3) !important;
}

/* Xóa gạch chân hover của menu thường cho nút CTA */
.btn-contact-nav::after {
    display: none !important;
}

/* 6. Responsive Mobile */
.menu-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
}

.menu-toggle span {
    width: 25px;
    height: 2px;
    background: var(--text-dark);
}

@media (max-width: 768px) {
    .main-navigation {
        display: none !important; /* Ẩn menu chính trên mobile để hiện toggle */
    }
    .menu-toggle {
        display: flex;
    }
}