html, body {
    height: 100%;
  }
  
  body {
    display: flex;
    flex-direction: column;
  }
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
  }
  
  body {
    font-family: Arial, sans-serif;
  }
  
  /* ===== HEADER ===== */
  .header {
    position: sticky;
    top: 0;
    background: #111;
    color: #fff;
    z-index: 1000;
  }
  
  .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 30px;
  }
  
  .logo {
    font-size: 24px;
  }
  
  .nav ul {
    display: flex;
    gap: 20px;
    list-style: none;
  }
  
  .nav a {
    color: #fff;
    text-decoration: none;
    padding-bottom: 5px;
  }
  
  .nav a.active {
    border-bottom: 2px solid rgb(251, 0, 255);
  }
  
  .menu-toggle {
    display: none;
    cursor: pointer;
    font-size: 26px;
  }
  
  /* ===== HERO ===== */
  .hero {
    position: relative;
    height: 90vh;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
    color: white;
  }
  
  /* Background */
  .hero-bg {
    position: absolute;
    inset: 0;
    background: linear-gradient(120deg, #00ffcc, #0066ff);
    animation: bgMove 6s infinite alternate;
    z-index: 1;
  }
  
  @keyframes bgMove {
    from { transform: scale(1); }
    to { transform: scale(1.2); }
  }
  
  /* Overlay */
  .hero-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.4);
    animation: overlayFade 1.5s ease forwards;
    z-index: 2;
  }
  
  @keyframes overlayFade {
    from { opacity: 0; }
    to { opacity: 1; }
  }
  
  /* Content */
  .hero-content {
    position: relative;
    z-index: 3;
    text-align: center;
    animation: contentUp 1.2s ease forwards;
  }
  
  .hero-content h1 {
    font-size: 48px;
    margin-bottom: 15px;
  }
  
  .hero-content p {
    font-size: 20px;
    margin-bottom: 25px;
  }
  
  @keyframes contentUp {
    from {
      opacity: 0;
      transform: translateY(40px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }
  
  .hero-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
  }
  
  /* ===== BUTTON ===== */
  .btn {
    padding: 10px 20px;
    background: cyan;
    border: none;
    color: #000;
    text-decoration: none;
    transition: 0.3s;
  }
  
  .btn:hover {
    box-shadow: 0 0 20px cyan;
  }
  
  /* ===== SERVICES / PORTFOLIO ===== */
  .services,
  .portfolio {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    padding: 40px;
  }
  
  .card {
    padding: 40px;
    background: #eee;
    text-align: center;
    transition: transform 0.3s;
  }
  
  .card:hover {
    transform: scale(1.1);
  }
  
  /* Flip Card */
  .flip-card {
    perspective: 1000px;
  }
  
  .flip-inner {
    transition: transform 0.6s;
    transform-style: preserve-3d;
  }
  
  .flip-card:hover .flip-inner {
    transform: rotateY(180deg);
  }
  
  .front,
  .back {
    padding: 50px;
    backface-visibility: hidden;
  }
  
  .back {
    transform: rotateY(180deg);
    background: #00ffcc;
  }
  
  /* ===== CONTACT ===== */
  .contact {
    display: flex;
    flex-direction: column;
    gap: 15px;
    padding: 40px;
  }
  
  /* ===== FOOTER ===== */
  .footer {
    text-align: center;
    padding: 15px;
    background: #111;
    color: #fff;
  }
  
  /* ===== MOBILE ===== */
  @media (max-width: 768px) {
    .nav ul {
      position: absolute;
      top: 60px;
      right: 0;
      flex-direction: column;
      background: #222;
      width: 200px;
      transform: translateX(100%);
      transition: 0.3s;
    }
  
    .nav ul.show {
      transform: translateX(0);
    }
  
    .menu-toggle {
      display: block;
    }
  }
  .flip-card:hover .flip-inner {
    transform: rotateY(180deg);
  }
  /* CONTACT – CLEAN VERSION */
.contact {
    max-width: 600px;
    margin: 80px auto;
    padding: 40px;
    background: #f9f9f9;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.08);
    text-align: center;
  }
  
  .contact h2 {
    font-size: 32px;
    margin-bottom: 10px;
  }
  
  .contact-desc {
    color: #666;
    margin-bottom: 30px;
  }
  
  .contact-form {
    display: flex;
    flex-direction: column;
    gap: 15px;
  }
  
  .contact-form input,
  .contact-form textarea {
    padding: 12px 15px;
    border-radius: 8px;
    border: 1px solid #ccc;
    font-size: 16px;
  }
  
  .contact-form input:focus,
  .contact-form textarea:focus {
    outline: none;
    border-color: cyan;
    box-shadow: 0 0 8px rgba(0,255,255,0.4);
  }
  
  .contact-form .btn {
    margin-top: 10px;
    padding: 12px;
    font-size: 16px;
    border-radius: 8px;
  }
  /* THANK YOU MESSAGE */
.thank-you {
    margin-top: 20px;
    color: #00c896;
    font-weight: bold;
    opacity: 0;
    transform: translateY(10px);
    transition: 0.5s ease;
    display: none;
  }
  
  /* SHOW STATE */
  .thank-you.show {
    display: block;
    opacity: 1;
    transform: translateY(0);
  }
  
  /* BUTTON NÂNG CAO HƠN */
  .btn {
    background: linear-gradient(135deg, #00ffd5, #00bfff);
    color: #000;
    font-weight: bold;
    letter-spacing: 1px;
  }
  
  .btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 25px rgba(0,255,255,0.6);
  }
  main {
    flex: 1;
  }
  .project-1 {
    background: red;
  }
  .project-2 {
    background: red;
  }
  .project-3 {
    background: red;
  }
      /* CONTACT HERO BACKGROUND */
.contact-hero {
    position: relative;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
  }
  
  /* LỚP NỀN */
  .contact-bg {
    position: absolute;
    inset: 0;
    background: linear-gradient(120deg, #6a11cb, #2575fc);
    animation: contactBgMove 6s infinite alternate;
    z-index: 1;
  }
  
  @keyframes contactBgMove {
    from { transform: scale(1); }
    to { transform: scale(1.15); }
  }
  
  /* LỚP PHỦ */
  .contact-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.45);
    z-index: 2;
  }
  
  /* HỘP FORM */
  .contact-box {
    position: relative;
    z-index: 3;
    background: #fff;
    padding: 50px;
    border-radius: 16px;
    width: 100%;
    max-width: 600px;
    box-shadow: 0 20px 50px rgba(0,0,0,0.25);
    text-align: center;
    animation: fadeUp 1.2s ease;
  }
  
  @keyframes fadeUp {
    from {
      opacity: 0;
      transform: translateY(40px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }
  .thank-you {
    margin-top: 15px;
    color: #00c9a7;
    display: none;
    font-weight: bold;
  }
     /* ===== PORTFOLIO BACKGROUND (NO IMAGE) ===== */
.page {
    min-height: 100vh;
  }
  
  .portfolio {
    min-height: 100vh;
    padding: 80px 40px;
  
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
    gap: 30px;
  
    background: linear-gradient(135deg, #0f2027, #203a43, #2c5364);
    background-size: 300% 300%;
    animation: bgMove 10s infinite alternate;
  }
  
  @keyframes bgMove {
    from { background-position: 0% 50%; }
    to   { background-position: 100% 50%; }
  }
  .front.card {
    height: 220px;
    border-radius: 16px;
    background: linear-gradient(135deg, #ffffff, #eaeaea);
    display: flex;
    align-items: center;
    justify-content: center;
  
    font-size: 22px;
    font-weight: bold;
    color: #333;
  
    box-shadow: 0 15px 30px rgba(0,0,0,0.15);
  }
  .project-1 {
    background: linear-gradient(135deg, #00ffcc, #00bfff);
  }
  
  .project-2 {
    background: linear-gradient(135deg, #ff9a9e, #fad0c4);
  }
  
  .project-3 {
    background: linear-gradient(135deg, #a18cd1, #fbc2eb);
  }
  .flip-card {
    perspective: 1200px;
  }
  
  .flip-inner {
    transition: transform 0.7s ease;
    transform-style: preserve-3d;
  }
  
  .flip-card:hover .flip-inner {
    transform: rotateY(180deg);
  }
  
  .front,
  .back {
    backface-visibility: hidden;
  }
  
  .back.card {
    background: #111;
    color: #fff;
    transform: rotateY(180deg);
  
    display: flex;
    align-items: center;
    justify-content: center;
  
    font-size: 18px;
    border-radius: 16px;
  }