.header-top {
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-family: sans-serif;
    width: 960px;
}
    header {
      background: #0f172a;
      color: #fff;
      padding: 2rem;
      text-align: center;
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
    }
    header h1 {
      font-size: 2.5rem;
      font-weight: 800;
    }
    header p {
      font-size: 1.2rem;
      margin-top: 0.5rem;
      margin-bottom: 0;
    }
.logo {
    height: 70px;
    width: auto
}
/* Menu start */
.main-nav {
  background-color: #0f172a;
  display: flex;
  margin: 0;
  max-width: 960px;
  padding: 10px 20px;
  font-family: sans-serif;
}
.main-nav > ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
}
.main-nav ul.dropdown-content {
    display: none;
    padding: 10px;
    flex-direction: column; /* vẫn giữ nếu có .dropdown:hover ul */
}
.main-nav ul li {
  position: relative; /* cần thiết để dropdown định vị tương đối */
}
.main-nav ul li a {
  text-decoration: none;
  font-weight: bold;
  color: #F0F2F5;
  padding: 10px 14px;
  display: block;
}
.main-nav ul li a:hover {
  color: #00B5E2;
}
/* Dropdown */
.dropdown {
  position: relative;
}

/* Mặc định: căn trái theo nút "Blog" */
.dropdown-content {
  display: none;
  list-style: none;
  position: absolute;
  top: 100%;
  left: 0;
  transform: none;
  min-width: 240px;
  background: #1A1D23;
  border: 1px solid #333;
  border-radius: 6px;
  padding: 8px 0;
  z-index: 999;
}

ul li {
  list-style: none;
}

/* Toggle dropdown bằng JS */
.dropdown.open .dropdown-content {
  display: block;
}

    .dropdown-content li a {
      color: #F0F2F5;
      padding: 10px 16px;
      display: block;
      white-space: nowrap;
    }

    .dropdown-content li a:hover {
      background-color: #2A2D33;
      color: #00B5E2;
      text-decoration: underline;
    }
    /* Menu end */

.header-cta {
    background: #2563eb;
    color: white;
    padding: 1rem 2rem;
    border-radius: 8px;
    display: inline-block;
    font-weight: 600;
    text-decoration: none;
    cursor: pointer;
}

.header-cta:hover {
  background-color: #1e40af;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.3);
}

@media screen and (max-width: 600px) {
    .header-top {
        flex-direction: column;
        width: 100%;
        margin-bottom: 1.5rem;
    }
    .cta {
        margin-top: 1.5rem;
    }
  .dropdown-content {
    left: 50%;
    transform: translateX(-60%);
  }
}