:root {
  --bg: #7cb82a;
  --bg-section: #6aab1c;
  --bg-card: #ffffff;
  --bg-nav: #1e3200;
  --red: #cc0000;
  --red-hover: #e00000;
  --yellow: #f5c200;
  --yellow-dark: #c49800;
  --text: #1a3000;
  --text-dim: #3d5a10;
  --text-card: #222222;
  --text-card-dim: #555555;
  --white: #ffffff;
  --border-card: rgba(0, 0, 0, 0.1);
  --border-nav: rgba(255, 255, 255, 0.12);
  --radius: 12px;
  --shadow: 0 6px 28px rgba(0, 0, 0, 0.18);
}

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

html {
  scroll-behavior: smooth;
}

body {
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', sans-serif;
  line-height: 1.65;
}

img {
  display: block;
  max-width: 100%;
}

/* ===== CONTAINER ===== */
.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ===== NAVBAR ===== */
.navbar {
  position: sticky;
  top: 0;
  z-index: 200;
  background: var(--bg-nav);
  border-bottom: 3px solid var(--red);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
  position: relative;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  flex-shrink: 0;
}

.logo-img {
  height: 44px;
  width: auto;
  border-radius: 6px;
  background: #fff;
  padding: 2px 4px;
  object-fit: contain;
}

.logo-text {
  color: var(--white);
  font-weight: 700;
  font-size: 1rem;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.75rem;
}

.nav-links a {
  color: rgba(255, 255, 255, 0.85);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  transition: color 0.2s;
  white-space: nowrap;
}

.nav-links a:hover {
  color: var(--yellow);
}

.btn-nav-cta {
  background: var(--red) !important;
  color: var(--white) !important;
  padding: 8px 20px !important;
  border-radius: 6px;
  font-weight: 700 !important;
  transition: background 0.2s !important;
}

.btn-nav-cta:hover {
  background: var(--red-hover) !important;
  color: var(--white) !important;
}

.hamburger {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
  z-index: 10;
}

.hamburger span {
  display: block;
  width: 26px;
  height: 2px;
  background: var(--white);
  border-radius: 2px;
  transition: all 0.3s ease;
}

/* ===== HERO ===== */
.hero {
  background: var(--bg-nav);
  min-height: 88vh;
  display: flex;
  align-items: center;
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
  align-items: center;
  padding-top: 4rem;
  padding-bottom: 4rem;
  width: 100%;
}

.hero-text {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.hero-visual img {
  width: 100%;
  border-radius: 16px;
  box-shadow: 0 16px 48px rgba(0, 0, 0, 0.5);
  border: 3px solid rgba(124, 184, 42, 0.3);
}

.hero-badge {
  display: inline-block;
  background: var(--red);
  color: #fff;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 2.5px;
  text-transform: uppercase;
  padding: 5px 14px;
  border-radius: 4px;
  margin-bottom: 1.4rem;
}

.hero h1 {
  font-size: clamp(1.9rem, 4.5vw, 3.25rem);
  font-weight: 900;
  color: var(--white);
  line-height: 1.15;
  margin-bottom: 1rem;
  text-transform: uppercase;
  text-shadow: 0 2px 16px rgba(0, 0, 0, 0.6);
  letter-spacing: -0.5px;
}

.hero-sub {
  color: #d4f0a0;
  font-size: 1.05rem;
  margin-bottom: 1.75rem;
  letter-spacing: 0.5px;
}

.hero-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-bottom: 2.25rem;
}

.chip {
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  color: var(--white);
  padding: 6px 16px;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 600;
  backdrop-filter: blur(4px);
}

.chip-highlight {
  background: var(--yellow);
  border-color: var(--yellow);
  color: #1a0e00;
}

.btn-hero {
  display: inline-block;
  background: var(--red);
  color: var(--white);
  text-decoration: none;
  font-size: 1.1rem;
  font-weight: 700;
  padding: 15px 36px;
  border-radius: 8px;
  transition: background 0.2s, transform 0.15s;
  box-shadow: 0 4px 24px rgba(204, 0, 0, 0.5);
  letter-spacing: 0.3px;
}

.btn-hero:hover {
  background: var(--red-hover);
  transform: translateY(-3px);
}

/* ===== SECTIONS ===== */
.section {
  padding: 5.5rem 0;
}

.section-dark {
  background: var(--bg-section);
}

.section-title {
  font-size: clamp(1.6rem, 3vw, 2.4rem);
  font-weight: 800;
  color: var(--text);
  text-align: center;
  margin-bottom: 0.6rem;
  letter-spacing: -0.3px;
  text-shadow: 0 1px 2px rgba(255, 255, 255, 0.3);
}

.section-title::after {
  content: '';
  display: block;
  width: 56px;
  height: 4px;
  background: var(--red);
  margin: 0.8rem auto 0;
  border-radius: 2px;
}

.section-sub {
  text-align: center;
  color: var(--text-dim);
  max-width: 620px;
  margin: 1.25rem auto 2rem;
  font-size: 1rem;
  font-weight: 500;
}

/* ===== FEATURES ===== */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
  margin-bottom: 2rem;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  padding: 2.25rem 1.75rem;
  text-align: center;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: var(--shadow);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 36px rgba(0, 0, 0, 0.22);
}

.feature-icon {
  font-size: 2.4rem;
  margin-bottom: 1rem;
  color: var(--red);
}

.feature-card h3 {
  color: var(--text-card);
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
}

.feature-card p {
  font-size: 0.9rem;
  color: var(--text-card-dim);
  line-height: 1.65;
}

.kit-showcase {
  text-align: center;
}

.kit-showcase img {
  max-width: 100%;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  margin: 0 auto;
  border: 3px solid rgba(255, 255, 255, 0.5);
}

/* ===== KITS ===== */
.kits-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.75rem;
  margin-bottom: 3rem;
}

.kit-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  overflow: hidden;
  position: relative;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: var(--shadow);
}

.kit-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 12px 36px rgba(0, 0, 0, 0.25);
}

.kit-card img {
  width: 100%;
  height: 270px;
  object-fit: cover;
  object-position: center;
}

.kit-badge {
  position: absolute;
  top: 14px;
  left: 14px;
  font-size: 0.72rem;
  font-weight: 800;
  padding: 4px 12px;
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 1.5px;
}

.kit-badge-premium {
  background: var(--yellow);
  color: #1a0e00;
}

.kit-badge-budget {
  background: #2e8b57;
  color: #fff;
}

.kit-info {
  padding: 1.5rem 1.75rem;
}

.kit-info h3 {
  color: var(--text-card);
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 1rem;
}

.kit-info ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.kit-info li {
  color: var(--text-card-dim);
  font-size: 0.88rem;
  padding-left: 1.4rem;
  position: relative;
  line-height: 1.5;
}

.kit-info li::before {
  content: '✓';
  color: #2e8b57;
  position: absolute;
  left: 0;
  font-weight: 700;
}

.video-embed-card {
  background: var(--bg-card);
  border-radius: var(--radius);
  padding: 1.75rem;
  border: 1px solid var(--border-card);
  box-shadow: var(--shadow);
}

.video-embed-card h3 {
  color: var(--text-card);
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 1.25rem;
}

.embed-video {
  width: 100%;
  border-radius: 8px;
  display: block;
  background: #000;
}

/* ===== XUP PAP ===== */
.xuppap-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.5rem;
  align-items: start;
}

.spec-badge {
  display: inline-block;
  background: var(--red);
  color: #fff;
  font-size: 0.72rem;
  font-weight: 800;
  padding: 5px 16px;
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  margin-bottom: 1.5rem;
}

.spec-block {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  padding: 1.4rem 1.6rem;
  margin-bottom: 1rem;
  box-shadow: var(--shadow);
}

.spec-block h3 {
  color: var(--red);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  font-weight: 700;
  margin-bottom: 0.8rem;
}

.spec-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}

.spec-list li {
  font-size: 0.88rem;
  color: var(--text-card-dim);
}

.spec-list strong {
  color: var(--text-card);
}

.bike-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.bike-tag {
  background: rgba(124, 184, 42, 0.15);
  border: 1px solid rgba(106, 171, 28, 0.4);
  color: #1a3000;
  padding: 4px 14px;
  border-radius: 20px;
  font-size: 0.8rem;
  font-weight: 600;
}

.spec-note {
  font-size: 0.88rem;
  color: var(--text-card-dim);
  line-height: 1.65;
}

.spec-note strong {
  color: var(--text-card);
}

.xuppap-img {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  position: sticky;
  top: 80px;
}

.xuppap-img img {
  width: 100%;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  object-fit: cover;
  aspect-ratio: 3 / 4;
  border: 3px solid rgba(255, 255, 255, 0.6);
}

/* ===== QUY TRINH ===== */
.phase-block {
  margin-bottom: 3.5rem;
}

.phase-title {
  color: var(--text);
  font-size: 1.2rem;
  font-weight: 700;
  margin-bottom: 1.75rem;
  padding-left: 1.1rem;
  border-left: 4px solid var(--red);
  text-shadow: 0 1px 2px rgba(255, 255, 255, 0.3);
}

.steps-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 1.25rem;
}

.step-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: var(--shadow);
}

.step-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 32px rgba(0, 0, 0, 0.22);
}

.step-card img {
  width: 100%;
  height: 200px;
  object-fit: cover;
  object-position: center;
}

.step-label {
  padding: 1.1rem 1.25rem;
}

.step-num {
  display: inline-block;
  background: var(--red);
  color: #fff;
  font-size: 0.68rem;
  font-weight: 700;
  padding: 2px 10px;
  border-radius: 4px;
  margin-bottom: 0.55rem;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.step-label p {
  font-size: 0.875rem;
  color: var(--text-card-dim);
  line-height: 1.55;
}

.tip-box {
  background: #fff9e6;
  border: 1px solid #f5c200;
  border-left: 4px solid var(--yellow-dark);
  border-radius: var(--radius);
  padding: 1.4rem 1.75rem;
  color: #4a3800;
  font-size: 0.9rem;
  line-height: 1.75;
  box-shadow: var(--shadow);
}

.tip-box strong {
  color: #7a5a00;
}

/* ===== VIDEOS ===== */
.videos-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 2rem;
}

.video-card {
  background: var(--bg-card);
  border: 1px solid var(--border-card);
  border-radius: var(--radius);
  overflow: hidden;
  display: grid;
  grid-template-columns: 260px 1fr;
  align-items: stretch;
  box-shadow: var(--shadow);
  transition: box-shadow 0.2s;
}

.video-card:hover {
  box-shadow: 0 10px 36px rgba(0, 0, 0, 0.22);
}

.video-card-meta {
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  justify-content: center;
  border-right: 1px solid var(--border-card);
}

.video-card h3 {
  color: var(--text-card);
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 0.6rem;
}

.video-desc {
  color: var(--text-card-dim);
  font-size: 0.84rem;
  line-height: 1.6;
}

.video-card .video-iframe-wrapper {
  padding-bottom: 0;
  height: 100%;
  min-height: 300px;
}

.video-card video {
  width: 100%;
  display: block;
  background: #000;
}

.video-iframe-wrapper {
  position: relative;
  padding-bottom: 56.25%;
  min-height: 360px;
  height: 0;
  overflow: hidden;
}

.video-iframe-wrapper iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: none;
}

/* ===== CONTACT ===== */
.section-contact {
  background: var(--bg-section);
  border-top: 4px solid var(--red);
  padding: 5rem 0;
}

.contact-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2.5rem;
  flex-wrap: wrap;
}

.contact-text h2 {
  font-size: clamp(1.5rem, 3vw, 2.1rem);
  font-weight: 800;
  color: var(--white);
  margin-bottom: 0.6rem;
}

.contact-text p {
  color: rgba(255, 255, 255, 0.85);
  max-width: 420px;
  font-size: 0.95rem;
}

.btn-contact {
  display: flex;
  align-items: center;
  gap: 1.1rem;
  background: var(--red);
  color: var(--white);
  text-decoration: none;
  padding: 1.25rem 2.25rem;
  border-radius: 10px;
  transition: background 0.2s, transform 0.15s;
  box-shadow: 0 4px 28px rgba(204, 0, 0, 0.5);
  white-space: nowrap;
  flex-shrink: 0;
}

.btn-contact:hover {
  background: var(--red-hover);
  transform: translateY(-3px);
}

.contact-icon {
  font-size: 2rem;
}

.contact-info {
  display: flex;
  flex-direction: column;
}

.contact-info small {
  font-size: 0.72rem;
  opacity: 0.8;
  letter-spacing: 0.5px;
  text-transform: uppercase;
}

.contact-info strong {
  font-size: 1.45rem;
  font-weight: 800;
  letter-spacing: 1px;
}

/* ===== FOOTER ===== */
.footer {
  background: var(--bg-nav);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  padding: 1.75rem 0;
  text-align: center;
  color: rgba(255, 255, 255, 0.5);
  font-size: 0.85rem;
}

/* ===== RESPONSIVE ===== */

/* Tablet rộng: xupap section xuống 1 cột */
@media (max-width: 900px) {
  .xuppap-grid {
    grid-template-columns: 1fr;
  }

  .xuppap-img {
    position: static;
    grid-template-columns: 1fr 1fr;
  }

  .xuppap-img img {
    aspect-ratio: 4 / 3;
  }
}

/* Tablet / mobile lớn */
@media (max-width: 768px) {
  .hamburger {
    display: flex;
  }

  .nav-links {
    display: none;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg-nav);
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 0.5rem 0 1rem;
    border-bottom: 2px solid var(--red);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
    z-index: 199;
  }

  .nav-links.open {
    display: flex;
  }

  .nav-links a {
    padding: 0.9rem 1.5rem;
    font-size: 1rem;
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 0;
  }

  .btn-nav-cta {
    margin: 0.75rem 1.25rem 0 !important;
    padding: 0.75rem 1.25rem !important;
    text-align: center;
    border-radius: 8px !important;
    border-bottom: none !important;
  }

  /* Hero 2 cột → 1 cột, ảnh lên trên */
  .hero-inner {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .hero-visual {
    order: -1;
  }

  .hero-visual img {
    max-height: 280px;
    object-fit: cover;
  }

  .hero-text {
    align-items: center;
    text-align: center;
  }

  .hero-chips {
    justify-content: center;
  }

  .section {
    padding: 3.5rem 0;
  }

  .section-sub {
    margin-bottom: 2.5rem;
  }

  /* Video card: stack doc tren mobile */
  .video-card {
    grid-template-columns: 1fr;
  }

  .video-card-meta {
    border-right: none;
    border-bottom: 1px solid var(--border-card);
    padding: 1.25rem;
  }

  .video-card .video-iframe-wrapper {
    padding-bottom: 56.25%;
    height: 0;
    min-height: unset;
  }

  /* Kit cards: 1 cột */
  .kits-grid {
    grid-template-columns: 1fr;
  }

  .kit-card img {
    height: 240px;
  }

  /* Contact */
  .contact-inner {
    flex-direction: column;
    text-align: center;
  }

  .contact-text p {
    margin: 0 auto;
  }

  .btn-contact {
    width: 100%;
    justify-content: center;
  }
}

/* Mobile nhỏ */
@media (max-width: 480px) {
  .container {
    padding: 0 1rem;
  }

  /* Hero */
  .hero {
    min-height: auto;
  }

  .hero-inner {
    padding-top: 2.5rem;
    padding-bottom: 2.5rem;
  }

  .hero h1 {
    font-size: 1.6rem;
  }

  .hero-sub {
    font-size: 0.9rem;
  }

  .chip {
    font-size: 0.8rem;
    padding: 5px 12px;
  }

  .btn-hero {
    display: block;
    text-align: center;
    font-size: 1rem;
    padding: 14px 20px;
  }

  /* Sections */
  .section {
    padding: 2.75rem 0;
  }

  .section-title {
    font-size: 1.45rem;
  }

  .section-sub {
    font-size: 0.9rem;
    margin-bottom: 2rem;
  }

  /* Features: 1 cột */
  .features-grid {
    grid-template-columns: 1fr;
  }

  .feature-card {
    padding: 1.5rem 1.25rem;
  }

  /* Steps: 2 cột nhỏ (2×2 grid trực quan) */
  .steps-grid {
    grid-template-columns: 1fr 1fr;
    gap: 0.75rem;
  }

  .step-card img {
    height: 190px;
  }

  .step-label {
    padding: 0.75rem 0.9rem;
  }

  .step-label p {
    font-size: 0.78rem;
  }

  .phase-title {
    font-size: 1rem;
  }

  /* Xupap images: 2 cột ngang */
  .xuppap-img {
    grid-template-columns: 1fr 1fr;
  }

  .xuppap-img img {
    aspect-ratio: 1;
  }

  /* Video embed full-width */
  .video-embed-card {
    padding: 1.25rem 1rem;
  }

  /* Spec blocks */
  .spec-block {
    padding: 1rem 1.1rem;
  }

  /* Tip box */
  .tip-box {
    padding: 1rem 1.1rem;
    font-size: 0.85rem;
  }

  /* Contact button */
  .btn-contact {
    padding: 1rem 1.5rem;
  }

  .contact-info strong {
    font-size: 1.25rem;
  }
}

/* Màn hình rất nhỏ (≤ 360px) */
@media (max-width: 360px) {
  .hero h1 {
    font-size: 1.35rem;
  }

  .chip {
    font-size: 0.75rem;
    padding: 4px 10px;
  }

  /* Steps xuống 1 cột để tránh quá chật */
  .steps-grid {
    grid-template-columns: 1fr;
  }

  .step-card img {
    height: 180px;
  }

  .xuppap-img {
    grid-template-columns: 1fr;
  }

  .kits-grid {
    grid-template-columns: 1fr;
  }
}