:root {
      --primary: #2563eb;
      --primary-hover: #1d4ed8;
      --primary-light: #eff6ff;
      --text-dark: #0f172a;
      --text-muted: #64748b;
      --bg-body: #f8fafc;
      --bg-surface: #ffffff;
      --border-color: #e2e8f0;
      --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
      --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
      --shadow-lg: 0 12px 28px -4px rgba(0,0,0,0.12);
      --radius-sm: 6px;
      --radius-md: 10px;
      --radius-lg: 16px;
      --font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
      --transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
    }

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


    

    img {

      width: 100%;

      height: auto;

    }/* RESET & CORES */

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

    body {

      font-family: system-ui, sans-serif;

      line-height: 1.6;

      background: oklch(0.97 0.01 200);

      color: oklch(0.2 0.02 200);

      padding: 15px;

    }



    /* HEADER SYSTEM */


     footer {

      max-width: 1400px;

      margin: 0 auto; /* Căn giữa toàn bộ trang web */  

      background: oklch(0.4 0.15 240);

      color: white;

      padding: 20px;

      border-radius: 8px;

      margin-bottom: 20px;

      text-align: center;

    }


    

    ul li {

     list-style-type: none; /* Xóa dấu chấm */

    }

    

    a{text-decoration:none;color:#000;}



    /* =======================================================

       BƯỚC 2 & 3: MEDIA QUERIES (Bố cục tổng thể trang)

       Tư duy Mobile-First: Viết cho Mobile trước, mở rộng sau

    ========================================================== */

    

    /* MẶC ĐỊNH: MOBILE (Màn hình dưới 768px) */

    .page-layout {

      display: grid;

      grid-template-columns: 1fr; /* Toàn bộ xếp thành 1 cột dọc */

      gap: 20px;



    }

    .col-3{width: 100%;float:left;}
    .col-7{width: 100%;float:left;}

    .clearfix{ clear:both; }



    .sidebar {

      background: oklch(0.9 0.02 240);

      padding: 20px;

      border-radius: 8px;

    }



    /* MÀN HÌNH TABLET (Từ 768px trở lên) */

    @media (min-width: 768px) {

      body { padding: 30px; }

      

      .page-layout {

        grid-template-columns: 250px 1fr; /* Chia làm 2 cột: Sidebar trái, Main phải */

      }



      .col-3{width: 30%;float:left;}
      .col-7{width: 70%;float:left;}


    }



    /* MÀN HÌNH DESKTOP LỚN (Từ 1200px trở lên) */

    @media (min-width: 1200px) {

      .page-layout {

        max-width: 1400px;

        margin: 0 auto; /* Căn giữa toàn bộ trang web */

        grid-template-columns: 300px 1fr; /* Sidebar rộng hơn một chút */

      }

      .col-3{width: 30%;float:left;}
      .col-7{width: 70%;float:left;}

    }





    /* =======================================================

       KẾT HỢP: CONTAINER QUERIES (Cho các linh kiện bên trong)

    ========================================================== */

    

    /* 1. Biến khu vực chứa danh sách bài viết thành một "Khung theo dõi" */

    .articles-grid {

      display: grid;

      grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); /* Tự chia cột linh hoạt */

      gap: 20px;

      

      /* Kích hoạt Container Query trên khung này */

      container-type: inline-size;

      container-name: grid-container;

    }



    /* 2. Thiết kế thẻ Bài viết (Component độc lập) */

    .article-card {

      background: white;

      border-radius: 8px;

      overflow: hidden;

      box-shadow: 0 4px 6px rgba(0,0,0,0.05);

      display: flex;

      flex-direction: column; /* Mặc định: Ảnh trên, chữ dưới */



      .card-thumb {

        background: oklch(0.6 0.18 200);

        aspect-ratio: 16 / 9;

        width: 100%;

      }



      .card-body {

        padding: 15px;

        h3 { margin-bottom: 8px; font-size: 1.2rem; }

        p { font-size: 0.9rem; color: oklch(0.5 0.01 200); }

      }

    }



    /* 3. Phản ứng theo độ rộng của Khung chứa (Chứ không phải màn hình) */

    /* Khi ô lưới giãn rộng ra hơn 550px (ví dụ: khi sang màn hình Desktop lớn hoặc lưới ít cột) */

    @container grid-container (min-width: 550px) {

      .article-card {

        flex-direction: row; /* Biến thành dạng nằm ngang: Ảnh trái, chữ phải */

        

        .card-thumb {

          width: 200px;

          aspect-ratio: 1 / 1; /* Chuyển ảnh thành hình vuông */

        }

        

        .card-body {

          flex: 1;

          display: flex;

          flex-direction: column;

          justify-content: center;

        }

      }

    }


/* --------------------- MENU ----------------------*/
/* --------------------- MENU ----------------------*/
/* --------------------- MENU ----------------------*/

   .navbar {
      background-color: var(--bg-surface);
      border-bottom: 1px solid var(--border-color);
      position: sticky;
      top: 0;
      z-index: 1000;
      box-shadow: var(--shadow-sm);
    }

    .nav-container {
      max-width: 1400px;
      margin: 0 auto; 
      padding: 0 1.5rem;
      height: 72px;
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    /* Brand Logo */
    .brand-logo {
      display: flex;
      align-items: center;
      gap: 0.75rem;
      text-decoration: none;
      font-weight: 700;
      font-size: 1.25rem;
      color: var(--text-dark);
    }

    .brand-icon {
      width: 38px;
      height: 38px;
      background: linear-gradient(135deg, var(--primary), #4f46e5);
      border-radius: var(--radius-md);
      display: flex;
      align-items: center;
      justify-content: center;
      color: white;
    }

    .brand-tag {
      font-size: 0.7rem;
      background-color: var(--primary-light);
      color: var(--primary);
      padding: 2px 6px;
      border-radius: 4px;
      border: 1px solid #bfdbfe;
      margin-left: 4px;
      font-weight: 600;
    }

    .nav-menu {
      display: flex;
      align-items: center;
      list-style: none;
      gap: 0.5rem;
    }

    .nav-item {
      position: relative;
    }

    .nav-link {
      display: flex;
      align-items: center;
      gap: 0.4rem;
      padding: 0.6rem 1rem;
      color: var(--text-dark);
      text-decoration: none;
      font-weight: 500;
      font-size: 0.95rem;
      border-radius: var(--radius-sm);
      transition: var(--transition);
      cursor: pointer;
      border: none;
      background: none;
      font-family: inherit;
    }

    .nav-link:hover, .nav-link:focus {
      background-color: var(--primary-light);
      color: var(--primary);
    }

    .arrow-icon {
      width: 14px;
      height: 14px;
      fill: currentColor;
      transition: transform 0.25s ease;
    }

    /* Level 2 Dropdown */
    .dropdown-level-2 {
      position: absolute;
      top: 100%;
      left: 0;
      min-width: 230px;
      background-color: var(--bg-surface);
      border: 1px solid var(--border-color);
      border-radius: var(--radius-md);
      box-shadow: var(--shadow-lg);
      padding: 0.5rem;
      list-style: none;
      opacity: 0;
      visibility: hidden;
      transform: translateY(10px);
      transition: var(--transition);
      z-index: 100;
    }

    .nav-item.has-dropdown:hover > .dropdown-level-2,
    .nav-item.has-dropdown:focus-within > .dropdown-level-2 {
      opacity: 1;
      visibility: visible;
      transform: translateY(4px);
    }

    .nav-item.has-dropdown:hover > .nav-link .arrow-icon {
      transform: rotate(180deg);
    }

    /* Level 3 Dropdown */
    .dropdown-item {
      position: relative;
    }

    .dropdown-link {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 0.6rem 0.8rem;
      color: var(--text-dark);
      text-decoration: none;
      font-size: 0.9rem;
      font-weight: 500;
      border-radius: var(--radius-sm);
      transition: var(--transition);
      width: 100%;
      text-align: left;
      border: none;
      background: none;
      cursor: pointer;
      font-family: inherit;
    }

    .dropdown-link:hover, .dropdown-link:focus {
      background-color: var(--primary-light);
      color: var(--primary);
    }

    .dropdown-level-3 {
      position: absolute;
      top: 0;
      left: 100%;
      min-width: 210px;
      background-color: var(--bg-surface);
      border: 1px solid var(--border-color);
      border-radius: var(--radius-md);
      box-shadow: var(--shadow-lg);
      padding: 0.5rem;
      list-style: none;
      opacity: 0;
      visibility: hidden;
      transform: translateX(10px);
      transition: var(--transition);
      z-index: 101;
      margin-left: 0.25rem;
    }

    .dropdown-item.has-dropdown:hover > .dropdown-level-3,
    .dropdown-item.has-dropdown:focus-within > .dropdown-level-3 {
      opacity: 1;
      visibility: visible;
      transform: translateX(0);
    }

    .dropdown-item.has-dropdown:hover > .dropdown-link .side-arrow {
      transform: translateX(3px);
    }

    /* Right Action Buttons */
    .nav-actions {
      display: flex;
      align-items: center;
      gap: 0.75rem;
    }

    .btn {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      padding: 0.55rem 1.1rem;
      font-size: 0.9rem;
      font-weight: 600;
      border-radius: var(--radius-sm);
      text-decoration: none;
      transition: var(--transition);
      cursor: pointer;
      border: none;
    }

    .btn-ghost {
      color: var(--text-dark);
      background: transparent;
    }

    .btn-ghost:hover {
      background-color: var(--bg-body);
    }

    .btn-primary {
      background-color: var(--primary);
      color: white;
    }

    .btn-primary:hover {
      background-color: var(--primary-hover);
      box-shadow: 0 4px 12px rgba(37, 99, 235, 0.25);
    }

    /* Hamburger Toggle Button */
    .hamburger-btn {
      display: none;
      background: none;
      border: none;
      padding: 0.5rem;
      cursor: pointer;
      color: var(--text-dark);
      border-radius: var(--radius-sm);
    }

    .hamburger-btn:hover {
      background-color: var(--bg-body);
    }

    .hamburger-icon {
      width: 24px;
      height: 24px;
      fill: currentColor;
    }

    @media (max-width: 992px) {
      .hamburger-btn {
        display: block;
      }

      .nav-actions {
        display: none;
      }

      .nav-menu {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        bottom: 0;
        background-color: var(--bg-surface);
        flex-direction: column;
        align-items: stretch;
        padding: 1.25rem;
        gap: 0.5rem;
        overflow-y: auto;
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: transform 0.3s ease, opacity 0.3s ease, visibility 0.3s ease;
        z-index: 999;
      }

      .nav-menu.is-active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
      }

      .nav-link {
        justify-content: space-between;
        width: 100%;
        padding: 0.8rem 1rem;
        font-size: 1rem;
        background-color: var(--bg-body);
      }

      /* Mobile Accordions override */
      .dropdown-level-2, 
      .dropdown-level-3 {
        position: static;
        box-shadow: none;
        border: none;
        border-left: 2px solid var(--border-color);
        border-radius: 0;
        padding: 0 0 0 1rem;
        margin: 0.25rem 0 0.25rem 0.5rem;
        opacity: 1;
        visibility: visible;
        transform: none;
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.35s ease-out;
      }

      .dropdown-level-2.is-expanded,
      .dropdown-level-3.is-expanded {
        max-height: 500px;
        transition: max-height 0.5s ease-in;
      }

      .nav-item.has-dropdown:hover > .dropdown-level-2,
      .dropdown-item.has-dropdown:hover > .dropdown-level-3 {
        transform: none;
      }

      .arrow-icon.is-rotated {
        transform: rotate(180deg) !important;
      }

      .mobile-actions {
        display: flex;
        flex-direction: column;
        gap: 0.75rem;
        margin-top: 1.5rem;
        padding-top: 1.5rem;
        border-top: 1px solid var(--border-color);
      }

      .mobile-actions .btn {
        width: 100%;
      }
    }

   
    }