:root {
    --bg-color: #0f172a;
    --sidebar-color: #020617;
    --content-color: #111827;
    --text-color: #e5e7eb;
    --secondary-text: #9ca3af;
    --accent-color: #38bdf8;
    --course-bg: #1f2937;
    --description-bg: #111827;
  }

  * { box-sizing: border-box; font-family: "Segoe UI", Tahoma, sans-serif; }

  body { min-height:100vh; margin:0; background-color: var(--bg-color); color: var(--text-color); }

  /* Sidebar */
  .sidebar { width:280px; background-color: var(--sidebar-color); padding:2rem 1.5rem; position:fixed; top:0; left:0; height:100%; overflow-y:auto; transition: transform 0.3s ease; }
  .sidebar h2 { color: var(--accent-color); margin-bottom:1rem; }
  .menu-item { margin-bottom:0.6rem; }
  .menu-title { cursor:pointer; padding:0.6rem 0.8rem; border-radius:8px; display:flex; justify-content:space-between; align-items:center; }
  .menu-title:hover { background: rgba(56, 189, 248, 0.15); }
  .arrow { transition: transform 0.2s ease; }
  .menu-item.active .arrow { transform: rotate(90deg); }
  .submenu { list-style:none; padding-left:1.2rem; margin:0.4rem 0 0.6rem 0; display:none; }
  .menu-item.active .submenu { display:block; }
  .submenu li { margin:0.3rem 0; }
  .submenu a { text-decoration:none; font-size:0.85rem; color: var(--secondary-text); }
  .submenu a:hover { color: var(--accent-color); }

  /* Hamburger */
  .menu-toggle { display:none; position: fixed; top:15px; left:15px; z-index:1001; background: var(--accent-color); border:none; color:#0f172a; font-size:1.5rem; padding:0.5rem 0.8rem; border-radius:8px; cursor:pointer; }

  /* Content */
  .content { flex:1; margin-left:280px; padding:2rem; transition: margin-left 0.3s ease; overflow-x:hidden; }

  .course-block { background: var(--course-bg); padding:0.7rem 1rem; border-radius:6px; margin-top:1rem; font-family: monospace; color: #38bdf8; word-break: break-word; }
  .description { background: var(--description-bg); padding:0.7rem 1rem; border-radius:6px; margin:0.4rem 0 1rem 0; color: var(--secondary-text); line-height:1.5; }

  /* Responsive */
  @media(max-width:768px){
    .sidebar { transform: translateX(-100%); }
    .sidebar.active { transform: translateX(0); }
    .menu-toggle { display:block; }
    .content { margin-left:0; padding:1rem; }
  }

  .footer { margin-top:2rem; font-size:0.8rem; color: var(--secondary-text); text-align:center; }

  .menu-list {
  list-style: none;
  padding: 0;
  margin: 0;
  margin-top:45px;
}

.menu-list li {
  margin: 8px 0;
}

.menu-list a {
  color: #fff;
  text-decoration: none;
  font-weight: 500;
}

.menu-list a:hover {
  color: #00bfff;
}

 .k8s-container {
      display: flex;
      gap: 20px;
      font-family: monospace;
    }

    .k8s-main {
      flex: 3;
      background: #1e1e1e;
      color: #fff;
      padding: 20px;
      border-radius: 12px;
    }

    .k8s-sidebar {
      flex: 1;
      background: #111;
      padding: 10px;
      border-radius: 12px;
      color: #fff;
    }

    #console {
      background: #111;
      padding: 10px;
      height: 240px;
      overflow-y: auto;
      margin-bottom: 10px;
    }

    #input {
      width: 100%;
      padding: 10px;
      background: #222;
      color: #fff;
      border: none;
      display: none;
    }

    .success { color: #4caf50; }
    .error { color: #f44336; }

    .mission-box {
      padding: 12px;
      border-radius: 8px;
      margin-bottom: 10px;
    }

    .mission-active { background: #ff9800; color: #000; }
    .mission-done { background: #2e7d32; }

    .mission-item {
      padding: 6px;
      margin-bottom: 4px;
      border-radius: 4px;
      font-size: 0.85rem;
    }

    .mission-old { background: #2e7d32; }
    .mission-current { background: #ff9800; color: #000; }
    .mission-next { background: #424242; }

    #topBar {
      display: flex;
      justify-content: space-between;
      margin-bottom: 10px;
      flex-wrap: wrap;
      gap: 10px;
    }

    #k8sTree {
      white-space: pre;
      margin-top: 10px;
      color: #ccc;
      font-size: 0.85rem;
    }

    .k8s-container button {
      background: #333;
      color: #fff;
      border: none;
      padding: 6px 12px;
      cursor: pointer;
    }

    .k8s-container button:hover {
      background: #555;
    }

    @media (max-width: 900px) {
      .k8s-container {
        flex-direction: column;
      }
    }

    .course-layout {
  display: flex;
  gap: 20px;
  align-items: flex-start;
}

.course-main {
  flex: 3;
}

.course-box {
  background: #111;
  color: #e5e7eb;
  padding: 20px;
  border-radius: 6px;
  min-height: 450px;
}

.course-box h3 {
  color: #38bdf8;
  margin-bottom: 10px;
}

.course-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 15px;
}

.course-nav button {
  padding: 6px 14px;
  background: #1a1a1a;
  border: 1px solid #333;
  color: #38bdf8;
  cursor: pointer;
  border-radius: 4px;
}

.course-nav button:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.course-sections {
  flex: 1;
  background: #1a1a1a;
  border: 1px solid #333;
  padding: 12px;
  border-radius: 6px;
  font-family: monospace;
  position: sticky;
  top: 70px;
}

.course-sections h4 {
  color: #38bdf8;
  margin-bottom: 10px;
  margin-top: 0;
}

.section-link {
  display: block;
  padding: 6px 8px;
  cursor: pointer;
  color: #e5e7eb;
  border-radius: 3px;
  margin-bottom: 4px;
}

.section-link:hover {
  background: #222;
}

.section-link.active {
  background: #38bdf8;
  color: #000;
}

@media (max-width: 900px) {
  .course-layout {
    flex-direction: column;
  }
  .course-sections {
    position: static;
    width: 100%;
  }
}