/* =====================================================
   LUXURY TECH MONOCHROME DESIGN SYSTEM — YOUTUBE PORTFOLIO
   Crafted to Apple, Linear, Stripe & OpenAI Interface Standards
   Palette: Day Theme / High-Contrast Obsidian & Crisp Zinc
   Fully Responsive: Mobile (320px) -> 4K Ultra-Wide
===================================================== */

:root {
  --bg-body: #fafafa;
  --bg-card: #ffffff;
  --bg-subtle: #f4f4f5;
  --bg-glass: rgba(255, 255, 255, 0.85);

  --border-card: #e4e4e7;
  --border-hover: #09090b;

  --text-main: #09090b;
  --text-body: #3f3f46;
  --text-muted: #71717a;
  --text-light: #a1a1aa;

  --primary-btn: #09090b;
  --primary-btn-hover: #18181b;

  /* Beautiful Layered Shadows */
  --shadow-sm: 0px 2px 3px -1px rgba(0,0,0,0.06), 0px 1px 0px 0px rgba(0,0,0,0.02), 0px 0px 0px 1px rgba(0,0,0,0.04);
  --shadow-card: 0px 0px 0px 1px rgba(0,0,0,0.06), 0px 1px 2px -0.5px rgba(0,0,0,0.04), 0px 3px 6px -1.5px rgba(0,0,0,0.03);
  --shadow-hover: 0px 0px 0px 1px rgba(9,9,11,0.12), 0px 3px 6px -1px rgba(0,0,0,0.05), 0px 8px 16px -3px rgba(0,0,0,0.06), 0px 20px 32px -6px rgba(0,0,0,0.05);

  --ease-spring: cubic-bezier(0.16, 1, 0.3, 1);
  --duration-micro: 0.15s;
  --duration-ui: 0.22s;

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Segoe UI', Roboto, sans-serif;
  --font-heading: 'Plus Jakarta Sans', 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

/* ================= RESET ================= */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  scroll-behavior: smooth;
  -webkit-tap-highlight-color: transparent;
}

/* Custom Sleek Scrollbar */
::-webkit-scrollbar {
  width: 6px;
  height: 6px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: rgba(0, 0, 0, 0.16);
  border-radius: 999px;
}
::-webkit-scrollbar-thumb:hover {
  background: rgba(0, 0, 0, 0.32);
}
* {
  scrollbar-width: thin;
  scrollbar-color: rgba(0, 0, 0, 0.16) transparent;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-body);
  color: var(--text-main);
  line-height: 1.65;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  min-height: 100vh;
}

::selection {
  background: #09090b;
  color: #ffffff;
}

h1, h2 {
  font-family: var(--font-heading);
  color: var(--text-main);
  letter-spacing: -0.03em;
  font-weight: 700;
  line-height: 1.3;
}

.section {
  padding: clamp(36px, 5vw, 64px) clamp(16px, 4vw, 32px);
  max-width: 1300px;
  margin: auto;
}

.gray {
  background: transparent;
}

/* ================= NAVBAR ================= */
.navbar {
  position: sticky;
  top: 0;
  z-index: 1000;
  background: var(--bg-glass);
  backdrop-filter: blur(20px) saturate(180%);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  border-bottom: 1px solid rgba(0, 0, 0, 0.07);
  height: 64px;
  display: flex;
  align-items: center;
  transition-property: background-color, border-color, box-shadow;
  transition-duration: var(--duration-ui);
  transition-timing-function: ease;
}

.nav-container {
  max-width: 1300px;
  width: 100%;
  margin: auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 clamp(16px, 4vw, 32px);
  gap: 12px;
}

.logo {
  font-size: clamp(16px, 2.2vw, 18px);
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.02em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

/* BACK BUTTON */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: #ffffff;
  color: var(--text-main);
  border: 1px solid var(--border-card);
  border-radius: 8px;
  padding: 7px 15px;
  cursor: pointer;
  font-size: 13px;
  font-weight: 600;
  min-height: 38px;
  box-shadow: var(--shadow-sm);
  transition-property: transform, border-color, background-color, box-shadow;
  transition-duration: var(--duration-ui);
  transition-timing-function: var(--ease-spring);
  white-space: nowrap;
}

.back-btn:hover {
  transform: translateY(-1px);
  border-color: #09090b;
  background: #fdfdfd;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.05);
}

.back-btn:active {
  transform: scale(0.96);
}

/* ================= HERO SECTION ================= */
.hero {
  text-align: center;
  padding: clamp(36px, 5vw, 56px) 16px clamp(24px, 4vw, 36px);
}

.hero h1 {
  font-size: clamp(28px, 4.4vw, 44px);
  font-weight: 700;
  letter-spacing: -0.035em;
  margin-bottom: 8px;
}

.hero p {
  color: var(--text-muted);
  font-size: clamp(14px, 2vw, 16px);
  font-weight: 500;
}

/* ================= SECTION TITLE ================= */
.section-title {
  text-align: center;
  font-size: clamp(22px, 3vw, 28px);
  font-weight: 700;
  margin-bottom: clamp(24px, 4vw, 36px);
  letter-spacing: -0.025em;
}

/* ================= DESIGN GRID ================= */
.design-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(min(100%, 280px), 1fr));
  gap: clamp(18px, 2.5vw, 26px);
}

/* ================= IMAGE CARDS ================= */
.design-grid img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  border-radius: 14px;
  background: #ffffff;
  border: 1px solid rgba(0, 0, 0, 0.08);
  box-shadow: var(--shadow-card);
  transition-property: transform, box-shadow, border-color, opacity;
  transition-duration: 0.5s, var(--duration-ui), var(--duration-ui), 0.5s;
  transition-timing-function: var(--ease-spring);
  cursor: pointer;
  display: block;
  opacity: 0;
  transform: translateY(20px);
  will-change: opacity, transform;
}

.design-grid img.show {
  opacity: 1;
  transform: translateY(0);
}

.design-grid img.show:hover {
  transform: translateY(-4px) scale(1.02);
  box-shadow: var(--shadow-hover);
  border-color: #09090b;
}

/* Banner image specific styling */
.section.gray .design-grid {
  grid-template-columns: 1fr;
  max-width: 960px;
  margin: 0 auto;
}

.section.gray .design-grid img {
  aspect-ratio: 16 / 5;
  min-height: 140px;
  border-radius: 16px;
}

/* ================= FOOTER ================= */
footer {
  background: #ffffff;
  color: var(--text-muted);
  text-align: center;
  padding: clamp(28px, 4vw, 40px) 20px;
  margin-top: 40px;
  border-top: 1px solid var(--border-card);
  font-size: 13.5px;
  padding-bottom: max(28px, env(safe-area-inset-bottom));
}

/* ================= RESPONSIVE DESIGN ================= */
@media (max-width: 768px) {
  .navbar {
    height: 58px;
  }

  .nav-container {
    padding: 0 16px;
  }

  .design-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .section.gray .design-grid img {
    aspect-ratio: 16 / 6;
  }
}

@media (max-width: 480px) {
  .nav-container {
    padding: 0 12px;
  }

  .logo {
    font-size: 15px;
    max-width: 60%;
  }

  .back-btn {
    padding: 6px 12px;
    font-size: 12px;
    min-height: 34px;
  }

  .hero {
    padding: 24px 8px 16px;
  }

  .hero h1 {
    font-size: 24px;
  }

  .hero p {
    font-size: 13.5px;
  }

  .section {
    padding: 24px 12px;
  }

  .section-title {
    font-size: 18px;
    margin-bottom: 20px;
  }
}