/* ===========================================
   Heat Vault — Premium Sneakers
   Vanilla CSS · Organized sections
   =========================================== */

/* ---------- CSS Variables ---------- */
:root {
  --bg: #ffffff;
  --bg-dark: #0a0a0c;
  --bg-soft: #f5f5f7;
  --text: #0a0a0c;
  --text-soft: #5a5a63;
  --text-invert: #ffffff;
  --border: #e6e6ea;

  --neon: #b6ff3c;       /* lime/neon green */
  --neon-glow: #b6ff3c80;
  --violet: #8a2be2;     /* purple */
  --violet-2: #b266ff;
  --orange: #ff7a18;     /* accent */

  --grad: linear-gradient(135deg, var(--neon) 0%, var(--violet) 60%, var(--orange) 100%);
  --grad-text: linear-gradient(135deg, var(--neon), var(--violet));

  --radius: 18px;
  --radius-sm: 12px;
  --shadow-sm: 0 4px 14px rgba(10,10,12,.06);
  --shadow-md: 0 10px 30px rgba(10,10,12,.10);
  --shadow-glow: 0 10px 40px rgba(182,255,60,.25);

  --container: 1200px;
  --ease: cubic-bezier(.22,.61,.36,1);
}

/* ---------- Reset ---------- */
* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; display: block; }
a { color: inherit; text-decoration: none; }
button { font: inherit; cursor: pointer; border: 0; background: none; color: inherit; }

h1, h2, h3, h4 {
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 700;
  letter-spacing: -0.02em;
  line-height: 1.1;
}

.container { max-width: var(--container); margin: 0 auto; padding: 0 24px; }
.section { padding: 100px 0; }
.section.dark { background: var(--bg-dark); color: var(--text-invert); }
.eyebrow {
  display: inline-block;
  font-family: 'Space Grotesk', sans-serif;
  font-size: 0.85rem;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--violet);
  margin-bottom: 14px;
}
.section.dark .eyebrow { color: var(--neon); }
.grad-text {
  background: var(--grad-text);
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
}
.section-head { text-align: center; max-width: 720px; margin: 0 auto 60px; }
.section-head h2 { font-size: clamp(2rem, 4vw, 3rem); }
.section-sub { color: var(--text-soft); margin-top: 14px; }
.section.dark .section-sub { color: #b5b5bf; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 14px 28px;
  border-radius: 999px;
  font-weight: 600;
  font-family: 'Space Grotesk', sans-serif;
  transition: all .3s var(--ease);
  white-space: nowrap;
}
.btn-primary {
  background: var(--text);
  color: var(--text-invert);
  box-shadow: var(--shadow-sm);
}
.btn-primary:hover {
  background: var(--neon);
  color: var(--text);
  box-shadow: var(--shadow-glow);
  transform: translateY(-2px);
}
.btn-outline {
  border: 1.5px solid currentColor;
  background: transparent;
}
.btn-outline:hover {
  background: var(--text);
  color: var(--text-invert);
  transform: translateY(-2px);
}
.btn-ghost {
  background: var(--neon);
  color: var(--text);
}
.btn-ghost:hover { box-shadow: var(--shadow-glow); transform: translateY(-2px); }
.btn-block { width: 100%; }

/* ---------- Loader ---------- */
.loader {
  position: fixed; inset: 0; z-index: 9999;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  background: var(--bg-dark);
  transition: opacity .6s var(--ease), visibility .6s var(--ease);
}
.loader.hidden { opacity: 0; visibility: hidden; }
.loader-logo img { width: 110px; animation: pulse 1.6s ease-in-out infinite; }
.loader-bar {
  width: 160px; height: 3px; background: #ffffff20; border-radius: 99px;
  margin-top: 24px; overflow: hidden;
}
.loader-bar span {
  display: block; width: 40%; height: 100%;
  background: var(--grad);
  animation: loaderSlide 1.2s ease-in-out infinite;
}
@keyframes loaderSlide {
  0% { transform: translateX(-100%); }
  100% { transform: translateX(350%); }
}
@keyframes pulse {
  0%,100% { transform: scale(1); filter: drop-shadow(0 0 0 var(--neon-glow)); }
  50% { transform: scale(1.05); filter: drop-shadow(0 0 24px var(--neon-glow)); }
}

/* ---------- Navbar ---------- */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(255,255,255,.7);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid transparent;
  transition: all .3s var(--ease);
}
.navbar.scrolled {
  background: rgba(255,255,255,.92);
  border-bottom-color: var(--border);
  box-shadow: var(--shadow-sm);
}
.nav-container {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 24px;
}
.nav-logo {
  display: flex; align-items: center; gap: 10px;
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 700; letter-spacing: 0.05em;
}
.nav-logo img { width: 38px; height: 38px; object-fit: contain; }
.nav-links { display: flex; align-items: center; gap: 32px; }
.nav-link {
  font-weight: 500; font-size: 0.95rem;
  position: relative; padding: 6px 0;
  transition: color .25s var(--ease);
}
.nav-link::after {
  content: ''; position: absolute; left: 0; right: 0; bottom: -4px;
  height: 2px; background: var(--grad-text);
  transform: scaleX(0); transform-origin: left;
  transition: transform .3s var(--ease);
}
.nav-link.active::after, .nav-link:hover::after { transform: scaleX(1); }
.nav-cta { padding: 10px 22px; font-size: 0.9rem; }
.hamburger {
  display: none; flex-direction: column; gap: 5px; padding: 8px;
}
.hamburger span {
  width: 26px; height: 2px; background: var(--text); border-radius: 2px;
  transition: all .3s var(--ease);
}
.hamburger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.hamburger.open span:nth-child(2) { opacity: 0; }
.hamburger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ---------- Hero ---------- */
.hero {
  position: relative; min-height: 100vh;
  padding: 140px 0 80px;
  display: flex; align-items: center;
  overflow: hidden;
}
.hero-bg-glow {
  position: absolute; top: -20%; right: -10%;
  width: 700px; height: 700px;
  background: radial-gradient(circle, var(--neon-glow), transparent 60%);
  filter: blur(80px); z-index: 0;
  animation: floatGlow 8s ease-in-out infinite;
}
@keyframes floatGlow {
  0%,100% { transform: translate(0,0); }
  50% { transform: translate(-30px, 30px); }
}
.hero-grid {
  position: relative; z-index: 1;
  display: grid; grid-template-columns: 1.1fr 1fr; gap: 60px; align-items: center;
}
.hero-text h1 {
  font-size: clamp(2.8rem, 6vw, 5.5rem);
  margin: 14px 0 20px;
}
.hero-sub { font-size: 1.15rem; color: var(--text-soft); max-width: 480px; }
.hero-cta { display: flex; gap: 14px; margin-top: 32px; flex-wrap: wrap; }
.hero-stats {
  display: flex; gap: 40px; margin-top: 50px;
  padding-top: 30px; border-top: 1px solid var(--border);
}
.hero-stats div { display: flex; flex-direction: column; }
.hero-stats strong {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.6rem; font-weight: 700;
}
.hero-stats span { font-size: 0.85rem; color: var(--text-soft); }

.hero-visual {
  position: relative; height: 500px;
  display: flex; align-items: center; justify-content: center;
}
.floating-ring {
  position: absolute; width: 420px; height: 420px;
  border-radius: 50%;
  background: var(--grad);
  opacity: 0.18; filter: blur(20px);
  animation: floatGlow 6s ease-in-out infinite;
}
.floating-dot {
  position: absolute; border-radius: 50%; background: var(--neon);
  box-shadow: 0 0 30px var(--neon-glow);
}
.d1 { width: 14px; height: 14px; top: 15%; left: 20%; animation: floatY 4s ease-in-out infinite; }
.d2 { width: 10px; height: 10px; bottom: 18%; right: 15%; background: var(--violet); box-shadow: 0 0 30px var(--violet); animation: floatY 5s ease-in-out infinite reverse; }
.d3 { width: 8px; height: 8px; top: 30%; right: 22%; background: var(--orange); animation: floatY 4.5s ease-in-out infinite; }
@keyframes floatY {
  0%,100% { transform: translateY(0); }
  50% { transform: translateY(-20px); }
}
.hero-sneaker {
  position: relative; z-index: 2;
  max-width: 520px; width: 100%;
  filter: drop-shadow(0 30px 50px rgba(0,0,0,.25));
  animation: floatY 5s ease-in-out infinite;
}

/* ---------- Brands ---------- */
.brand-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 18px;
}
.brand-card {
  padding: 36px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-align: center;
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 600; font-size: 1.1rem;
  background: var(--bg);
  transition: all .3s var(--ease);
}
.brand-card:hover {
  transform: translateY(-6px);
  border-color: var(--neon);
  box-shadow: var(--shadow-glow);
  color: var(--violet);
}

/* ---------- Filters ---------- */
.filters {
  display: flex; gap: 20px; align-items: center; justify-content: space-between;
  margin-bottom: 50px; flex-wrap: wrap;
}
.search-input {
  flex: 1; min-width: 240px; max-width: 360px;
  padding: 14px 22px;
  background: #1a1a1f;
  border: 1px solid #2a2a32;
  border-radius: 999px;
  color: var(--text-invert);
  font-family: inherit;
  transition: all .25s var(--ease);
}
.search-input:focus {
  outline: none; border-color: var(--neon);
  box-shadow: 0 0 0 4px rgba(182,255,60,.15);
}
.search-input::placeholder { color: #7a7a85; }
.filter-chips { display: flex; gap: 10px; flex-wrap: wrap; }
.chip {
  padding: 10px 18px;
  border-radius: 999px;
  background: #1a1a1f;
  border: 1px solid #2a2a32;
  color: #c5c5cc;
  font-size: 0.9rem; font-weight: 500;
  transition: all .25s var(--ease);
}
.chip:hover { color: var(--neon); border-color: var(--neon); }
.chip.active {
  background: var(--neon); color: var(--text); border-color: var(--neon);
  box-shadow: var(--shadow-glow);
}

/* ---------- Product Grid ---------- */
.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
}
.product-card {
  background: #14141a;
  border: 1px solid #22222a;
  border-radius: var(--radius);
  padding: 20px;
  display: flex; flex-direction: column;
  transition: transform .35s var(--ease), box-shadow .35s var(--ease), border-color .35s var(--ease);
  transform-style: preserve-3d;
  cursor: pointer;
}
.product-card:hover {
  border-color: var(--neon);
  box-shadow: 0 20px 40px rgba(0,0,0,.4), 0 0 30px rgba(182,255,60,.15);
}
.product-image {
  aspect-ratio: 1 / 1;
  background: linear-gradient(135deg, #1f1f26, #0e0e12);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  overflow: hidden; position: relative;
  margin-bottom: 18px;
}
.product-image img {
  width: 85%; height: 85%; object-fit: contain;
  transition: transform .5s var(--ease);
}
.product-card:hover .product-image img { transform: rotate(-8deg) scale(1.08); }
.brand-tag {
  display: inline-block;
  font-size: 0.7rem; letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--neon); font-weight: 600;
  margin-bottom: 6px;
}
.product-name {
  font-family: 'Space Grotesk', sans-serif;
  font-weight: 600; font-size: 1rem;
  color: var(--text-invert);
  margin-bottom: 4px;
}
.product-price {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.1rem; font-weight: 700;
  color: var(--violet-2);
  margin-bottom: 14px;
}
.product-btn {
  margin-top: auto;
  padding: 10px 16px;
  background: transparent;
  border: 1px solid #2e2e38;
  border-radius: 999px;
  color: var(--text-invert);
  font-weight: 500; font-size: 0.85rem;
  transition: all .25s var(--ease);
}
.product-card:hover .product-btn {
  background: var(--neon); color: var(--text); border-color: var(--neon);
}
.empty-state { text-align: center; color: #8a8a93; padding: 40px 0; }

/* ---------- About ---------- */
.about-grid {
  display: grid; grid-template-columns: 1.1fr 1fr;
  gap: 60px; align-items: center;
}
.about-grid h2 { font-size: clamp(2rem, 4vw, 3rem); margin: 14px 0 20px; }
.about-grid p { color: var(--text-soft); font-size: 1.05rem; margin-bottom: 28px; }
.about-card {
  padding: 50px 40px;
  border-radius: var(--radius);
  background: var(--bg-dark); color: var(--text-invert);
  position: relative; overflow: hidden;
}
.about-card.glow::before {
  content: ''; position: absolute; inset: -1px;
  background: var(--grad); border-radius: inherit; z-index: -1;
  filter: blur(20px); opacity: .4;
}
.about-card h3 {
  font-size: 1.5rem; margin-bottom: 10px;
  background: var(--grad-text);
  -webkit-background-clip: text; background-clip: text; color: transparent;
}

/* ---------- Why ---------- */
.why-grid {
  display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px;
}
.why-card {
  padding: 32px 28px;
  border-radius: var(--radius);
  background: #14141a;
  border: 1px solid #22222a;
  transition: all .35s var(--ease);
}
.why-card:hover {
  transform: translateY(-6px);
  border-color: var(--neon);
  box-shadow: var(--shadow-glow);
}
.why-icon {
  width: 56px; height: 56px;
  border-radius: 14px;
  background: var(--grad);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.6rem; margin-bottom: 18px;
}
.why-card h3 { font-size: 1.15rem; margin-bottom: 8px; }
.why-card p { color: #b5b5bf; font-size: 0.95rem; }

/* ---------- Testimonials ---------- */
.testi-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.testi-card {
  padding: 32px;
  border-radius: var(--radius);
  background: var(--bg-soft);
  border: 1px solid var(--border);
  transition: all .35s var(--ease);
}
.testi-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--violet);
}
.testi-card p { font-size: 1rem; margin-bottom: 20px; }
.testi-meta { display: flex; flex-direction: column; }
.testi-meta strong { font-family: 'Space Grotesk', sans-serif; }
.testi-meta span { font-size: 0.85rem; color: var(--text-soft); }

/* ---------- FAQ ---------- */
.faq-list { max-width: 760px; margin: 0 auto; display: flex; flex-direction: column; gap: 14px; }
.faq-item {
  background: #14141a;
  border: 1px solid #22222a;
  border-radius: var(--radius-sm);
  padding: 20px 24px;
  transition: border-color .25s var(--ease);
}
.faq-item[open] { border-color: var(--neon); }
.faq-item summary {
  cursor: pointer; font-weight: 600; font-family: 'Space Grotesk', sans-serif;
  list-style: none; display: flex; justify-content: space-between; align-items: center;
}
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::after {
  content: '+'; font-size: 1.5rem; color: var(--neon);
  transition: transform .3s var(--ease);
}
.faq-item[open] summary::after { transform: rotate(45deg); }
.faq-item p { margin-top: 12px; color: #b5b5bf; }

/* ---------- Footer ---------- */
.footer {
  background: var(--bg-dark); color: var(--text-invert);
  padding: 70px 0 30px;
}
.footer-grid {
  display: grid; grid-template-columns: 1.4fr 1fr 1fr; gap: 50px;
}
.footer .nav-logo { color: var(--text-invert); margin-bottom: 14px; }
.footer-tag { color: #b5b5bf; }
.footer h4 {
  font-size: 1rem; margin-bottom: 16px; color: var(--neon);
  font-family: 'Space Grotesk', sans-serif;
}
.footer a { display: block; color: #c5c5cc; margin-bottom: 10px; transition: color .2s; }
.footer a:hover { color: var(--neon); }
.footer-bottom {
  text-align: center; padding-top: 30px; margin-top: 50px;
  border-top: 1px solid #22222a; color: #7a7a85; font-size: 0.85rem;
}

/* ---------- Modal ---------- */
.modal {
  position: fixed; inset: 0; z-index: 200;
  display: none; align-items: center; justify-content: center;
  padding: 20px;
}
.modal.open { display: flex; animation: fadeIn .3s var(--ease); }
.modal-backdrop {
  position: absolute; inset: 0;
  background: rgba(0,0,0,.75);
  backdrop-filter: blur(8px);
}
.modal-panel {
  position: relative; z-index: 1;
  background: var(--bg);
  border-radius: 24px;
  max-width: 880px; width: 100%;
  max-height: 90vh; overflow-y: auto;
  animation: scaleIn .35s var(--ease);
  box-shadow: 0 40px 80px rgba(0,0,0,.4);
}
.modal-close {
  position: absolute; top: 16px; right: 18px; z-index: 2;
  width: 36px; height: 36px; border-radius: 50%;
  background: var(--bg-soft);
  font-size: 1.4rem; line-height: 1;
  transition: all .2s var(--ease);
}
.modal-close:hover { background: var(--text); color: var(--text-invert); transform: rotate(90deg); }
.modal-grid {
  display: grid; grid-template-columns: 1fr 1fr; gap: 0;
}
.modal-image {
  background: linear-gradient(135deg, #f5f5f7, #e8e8ec);
  display: flex; align-items: center; justify-content: center;
  padding: 40px; min-height: 360px;
  border-radius: 24px 0 0 24px;
}
.modal-image img { max-width: 100%; max-height: 320px; object-fit: contain; }
.modal-info { padding: 40px; }
.modal-info .brand-tag { color: var(--violet); }
.modal-info h3 {
  font-size: 1.8rem; margin: 8px 0 10px;
}
.modal-price {
  font-family: 'Space Grotesk', sans-serif;
  font-size: 1.6rem; font-weight: 700;
  color: var(--violet);
  margin-bottom: 26px;
}
.modal-label {
  font-size: 0.8rem; letter-spacing: 0.12em; text-transform: uppercase;
  color: var(--text-soft); margin-bottom: 12px;
}
.size-grid {
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-bottom: 24px;
}
.size-btn {
  padding: 12px 0;
  border: 1.5px solid var(--border);
  border-radius: 10px;
  font-weight: 600; font-size: 0.9rem;
  transition: all .2s var(--ease);
}
.size-btn:hover { border-color: var(--text); }
.size-btn.selected {
  background: var(--text); color: var(--text-invert); border-color: var(--text);
}
.modal-note { font-size: 0.8rem; color: var(--text-soft); margin-top: 14px; text-align: center; }

@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
@keyframes scaleIn {
  from { opacity: 0; transform: scale(.94) translateY(10px); }
  to { opacity: 1; transform: scale(1) translateY(0); }
}

/* ---------- Back to top ---------- */
.back-top {
  position: fixed; bottom: 28px; right: 28px; z-index: 90;
  width: 48px; height: 48px; border-radius: 50%;
  background: var(--text); color: var(--text-invert);
  font-size: 1.2rem; font-weight: 700;
  box-shadow: var(--shadow-md);
  opacity: 0; visibility: hidden;
  transition: all .3s var(--ease);
}
.back-top.show { opacity: 1; visibility: visible; }
.back-top:hover { background: var(--neon); color: var(--text); box-shadow: var(--shadow-glow); transform: translateY(-4px); }

/* ---------- Reveal animations ---------- */
.reveal {
  opacity: 0; transform: translateY(30px);
  transition: opacity .8s var(--ease), transform .8s var(--ease);
}
.reveal.visible { opacity: 1; transform: translateY(0); }

/* ---------- Responsive ---------- */
@media (max-width: 960px) {
  .hero-grid, .about-grid { grid-template-columns: 1fr; gap: 40px; }
  .hero-visual { height: 380px; order: -1; }
  .hero-sneaker { max-width: 380px; }
  .brand-grid { grid-template-columns: repeat(3, 1fr); }
  .why-grid, .testi-grid { grid-template-columns: repeat(2, 1fr); }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .modal-grid { grid-template-columns: 1fr; }
  .modal-image { border-radius: 24px 24px 0 0; min-height: 260px; }
}

@media (max-width: 720px) {
  .section { padding: 70px 0; }
  .hamburger { display: flex; }
  .nav-links {
    position: fixed; top: 70px; right: 0;
    width: 80%; max-width: 320px; height: calc(100vh - 70px);
    background: var(--bg);
    flex-direction: column; align-items: flex-start;
    padding: 40px 30px; gap: 24px;
    border-left: 1px solid var(--border);
    transform: translateX(100%);
    transition: transform .35s var(--ease);
    box-shadow: -10px 0 30px rgba(0,0,0,.08);
  }
  .nav-links.open { transform: translateX(0); }
  .nav-cta { width: 100%; text-align: center; }
  .hero-stats { gap: 24px; }
  .why-grid, .testi-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: 30px; }
  .size-grid { grid-template-columns: repeat(4, 1fr); }
  .filters { flex-direction: column; align-items: stretch; }
  .search-input { max-width: 100%; }
}