body {             margin: 0;             font-family: Arial, sans-serif;             background: #f4f6f8;             color: #222;         }          header {             background: #1f2937;             color: #fff;             padding: 20px;         }          header h1 {             margin: 0;             font-size: 24px;         }          /* TOP MENU (динамический) */         .top-menu {             background: #374151;             padding: 10px 20px;         }          .top-menu ul {             list-style: none;             margin: 0;             padding: 0;             display: flex;             gap: 15px;         }          .top-menu a {             color: #e5e7eb;             text-decoration: none;         }          .top-menu a:hover {             color: #fff;         }          /* BANNER */         #banner {             display: block;             max-height: 250px;             overflow: hidden;         }          #banner img {             width: 100%;             display: block;         }          main {             max-width: 1200px;             margin: auto;             padding: 20px;             display: flex;             gap: 20px;         }          article {             flex: 3;             background: #fff;             padding: 20px;             border-radius: 10px;             line-height: 1.6;         }          /* TOC */         nav {             flex: 1;             background: #fff;             padding: 15px;             border-radius: 10px;             height: fit-content;             position: sticky;             top: 20px;         }          nav ul {             list-style: none;             margin: 0;             padding: 0;         }          nav li {             margin-bottom: 10px;         }          nav a {             text-decoration: none;             color: #374151;             font-size: 14px;         }          nav a:hover {             color: #2563eb;         }          footer {             text-align: center;             padding: 20px;             background: #1f2937;             color: #ccc;             margin-top: 30px;         }          @media (max-width: 900px) {             main {                 flex-direction: column;             }              nav {                 position: static;             }         }body {     margin: 0;     font-family: 'Segoe UI', Arial, sans-serif;     background: #f4f6f8;     color: #333; }  /* HEADER */ header {     background: linear-gradient(135deg, #1e293b, #334155);     color: #fff;     padding: 25px 20px;     box-shadow: 0 2px 8px rgba(0,0,0,0.1); }  header h1 {     margin: 0;     font-size: 28px; }  /* TOP MENU */ .top-menu {     display: flex;     gap: 20px;     padding: 12px 20px;     background: #0f172a; }  .top-menu a {     color: #cbd5f5;     text-decoration: none;     font-weight: 500;     transition: 0.2s; }  .top-menu a:hover {     color: #fff; }  /* BANNER */ #banner {     display: block;     max-height: 260px;     overflow: hidden; }  #banner img {     width: 100%;     height: auto;     display: block; }  /* MAIN LAYOUT */ main {     display: flex;     gap: 25px;     padding: 25px;     max-width: 1200px;     margin: auto; }  /* ARTICLE */ article {     flex: 3;     background: #fff;     padding: 25px;     border-radius: 12px;     box-shadow: 0 4px 15px rgba(0,0,0,0.05);     line-height: 1.6; }  /* Заголовки внутри контента */ article h1,  article h2,  article h3 {     margin-top: 25px;     color: #1e293b; }  /* TOC */ nav {     flex: 1;     background: #fff;     padding: 20px;     border-radius: 12px;     box-shadow: 0 4px 15px rgba(0,0,0,0.05);     position: sticky;     top: 20px;     height: fit-content; }  /* Заголовок TOC */ nav::before {     content: "Содержание";     display: block;     font-weight: bold;     margin-bottom: 15px;     font-size: 16px; }  /* список */ nav ul {     list-style: none;     padding: 0;     margin: 0; }  nav li {     margin-bottom: 10px; }  /* ссылки */ nav a {     text-decoration: none;     color: #334155;     font-size: 14px;     transition: 0.2s; }  nav a:hover {     color: #2563eb;     padding-left: 5px; }  /* FOOTER */ footer {     text-align: center;     padding: 25px;     background: #1e293b;     color: #cbd5f5;     margin-top: 40px; }  /* АДАПТИВ */ @media (max-width: 900px) {     main {         flex-direction: column;     }      nav {         position: static;     } }