/* ========================================
   YANU Landing Page — Design Tokens
   ======================================== */

:root {
  /* Colors — YANU palette */
  --accent: #306E6F;
  --accent-hover: #275a5b;
  --dark-bg: #1C1C1E;
  --light-bg: #F7F7F7;
  --white: #FFFFFF;
  --black: #000000;
  --text-primary-light: #000000;
  --text-primary-dark: #FFFFFF;
  --text-secondary-light: #888888;
  --text-secondary-dark: #8E8E93;
  --card-border: #E5E7EB;

  /* Grade color spectrum — decorative */
  --grade-easy: #C8D4C8;
  --grade-mid: #306E6F;
  --grade-hard: #8B6F5C;
  --grade-peak: #3A2018;

  /* Typography */
  --font-sans: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'DM Mono', 'SF Mono', monospace;

  /* Layout */
  --max-width: 1080px;
  --section-padding: 120px 24px;
  --section-padding-mobile: 80px 20px;
}

/* ========================================
   Reset & Base
   ======================================== */

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-sans);
  font-size: 17px;
  font-weight: 400;
  line-height: 1.47;
  letter-spacing: -0.2px;
  color: var(--text-primary-light);
  background: var(--white);
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: opacity 0.2s;
}

a:hover {
  opacity: 0.8;
}

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

/* ========================================
   Navigation — Frosted Glass
   ======================================== */

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: 52px;
  background: rgba(28, 28, 30, 0.82);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
}

.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
}

.nav-logo {
  font-size: 20px;
  font-weight: 900;
  color: var(--white);
  letter-spacing: -0.5px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.nav-logo img {
  width: 28px;
  height: 28px;
  border-radius: 6px;
  filter: brightness(0) invert(1);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  font-size: 13px;
  font-weight: 400;
  color: rgba(255, 255, 255, 0.8);
  letter-spacing: 0;
  transition: color 0.2s;
}

.nav-links a:hover {
  color: var(--white);
  opacity: 1;
}

.nav-cta {
  font-size: 13px !important;
  font-weight: 500 !important;
  color: var(--white) !important;
  background: var(--accent);
  padding: 6px 16px;
  border-radius: 980px;
  transition: background 0.2s !important;
}

.nav-cta:hover {
  background: var(--accent-hover) !important;
  opacity: 1 !important;
}

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 18px;
  height: 1.5px;
  background: rgba(255, 255, 255, 0.8);
  margin: 4px 0;
  transition: transform 0.3s, opacity 0.3s;
}

/* ========================================
   Sections — Shared
   ======================================== */

.section {
  padding: var(--section-padding);
}

.section-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

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

.section--light {
  background: var(--light-bg);
  color: var(--text-primary-light);
}

.section--white {
  background: var(--white);
  color: var(--text-primary-light);
}

/* ========================================
   Typography
   ======================================== */

.headline-hero {
  font-size: 56px;
  font-weight: 900;
  line-height: 1.07;
  letter-spacing: -1.5px;
}

.headline-section {
  font-size: 40px;
  font-weight: 900;
  line-height: 1.10;
  letter-spacing: -0.5px;
}

.headline-feature {
  font-size: 21px;
  font-weight: 700;
  line-height: 1.19;
}

.text-body {
  font-size: 17px;
  font-weight: 400;
  line-height: 1.47;
  letter-spacing: -0.2px;
}

.text-secondary {
  color: var(--text-secondary-light);
}

.text-secondary-dark {
  color: rgba(255, 255, 255, 0.7);
}

.text-caption {
  font-size: 14px;
  line-height: 1.43;
}

.text-micro {
  font-size: 12px;
  line-height: 1.33;
}

/* ========================================
   Pill Button
   ======================================== */

.btn-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-sans);
  font-size: 17px;
  font-weight: 500;
  padding: 14px 32px;
  border-radius: 980px;
  border: none;
  cursor: pointer;
  transition: background 0.2s, transform 0.15s;
  text-decoration: none;
}

.btn-pill:hover {
  opacity: 1;
  transform: scale(1.02);
}

.btn-pill:active {
  transform: scale(0.98);
}

.btn-pill--accent {
  background: var(--accent);
  color: var(--white);
}

.btn-pill--accent:hover {
  background: var(--accent-hover);
}

.btn-pill--outline {
  background: transparent;
  color: var(--accent);
  border: 1.5px solid var(--accent);
}

.btn-pill--outline-light {
  background: transparent;
  color: var(--white);
  border: 1.5px solid rgba(255, 255, 255, 0.3);
}

.btn-pill--outline-light:hover {
  border-color: rgba(255, 255, 255, 0.6);
}

/* Apple App Store badge style */
.btn-appstore {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  background: var(--white);
  color: var(--black);
  padding: 12px 28px;
  border-radius: 980px;
  font-size: 15px;
  font-weight: 500;
  text-decoration: none;
  transition: background 0.2s, transform 0.15s;
}

.btn-appstore:hover {
  background: rgba(255, 255, 255, 0.9);
  opacity: 1;
  transform: scale(1.02);
}

.btn-appstore svg {
  width: 20px;
  height: 20px;
}

/* ========================================
   Hero Section
   ======================================== */

/* Hero wrapper creates scroll room for the phone entrance */
.hero-wrapper {
  height: 180vh;
  position: relative;
}

.hero {
  padding-top: 160px;
  padding-bottom: 80px;
  text-align: center;
  min-height: 100vh;
  display: flex;
  align-items: center;
  position: sticky;
  top: 0;
  overflow: hidden;
  background: var(--dark-bg);
  color: var(--text-primary-dark);
}

/* Carousel slides */
.hero-bg-slide {
  position: absolute;
  inset: 0;
  background-size: cover;
  background-position: center;
  opacity: 0;
  animation: heroFade 18s infinite;
}

.hero-bg-slide--1 {
  background-image: url('/assets/hero-bg-1.jpg');
  animation-delay: 0s;
}

.hero-bg-slide--2 {
  background-image: url('/assets/hero-bg-2.JPG');
  animation-delay: 6s;
}

.hero-bg-slide--3 {
  background-image: url('/assets/hero-bg-3.JPG');
  animation-delay: 12s;
}

@keyframes heroFade {
  0%      { opacity: 0; }
  5%      { opacity: 1; }
  33.33%  { opacity: 1; }
  38.33%  { opacity: 0; }
  100%    { opacity: 0; }
}

/* Dark overlay on top of slides */
.hero-overlay {
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, rgba(0, 0, 0, 0.7), rgba(28, 28, 30, 0.92));
  z-index: 1;
}

.hero .section-inner {
  width: 100%;
  position: relative;
  z-index: 2;
}

.hero-subtitle {
  font-size: 19px;
  font-weight: 500;
  line-height: 1.47;
  color: #FFFFFF;
  max-width: 520px;
  margin: 20px auto 40px;
  text-shadow: 0 1px 8px rgba(0, 0, 0, 0.6);
}

.hero-cta {
  display: flex;
  justify-content: center;
  gap: 16px;
  margin-bottom: 64px;
}

.hero-mockup {
  max-width: 320px;
  margin: 0 auto;
}

/* Hero phone starts off-screen, animated by scroll JS */
.hero-mockup .screenshot-placeholder {
  transform: translateY(100%);
  opacity: 0;
  will-change: transform, opacity;
  transition: none;
}

/* Screenshot placeholder */
.screenshot-placeholder {
  aspect-ratio: 9 / 19.5;
  max-width: 280px;
  background: #2C2C2E;
  border-radius: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto;
  border: 1px solid rgba(255, 255, 255, 0.08);
  position: relative;
  overflow: hidden;
}

.screenshot-placeholder::before {
  content: '';
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 120px;
  height: 28px;
  background: var(--dark-bg);
  border-radius: 0 0 16px 16px;
}

.screenshot-placeholder span {
  font-size: 13px;
  font-weight: 500;
  color: rgba(255, 255, 255, 0.2);
  letter-spacing: 2px;
  text-transform: uppercase;
}

/* Light variant */
.screenshot-placeholder--light {
  background: #E8E8ED;
  border-color: rgba(0, 0, 0, 0.06);
}

.screenshot-placeholder--light::before {
  background: var(--light-bg);
}

.screenshot-placeholder--light span {
  color: rgba(0, 0, 0, 0.15);
}

/* ========================================
   Features Grid
   ======================================== */

.features-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-top: 64px;
}

.feature-card {
  background: var(--white);
  border-radius: 14px;
  padding: 32px 24px;
  text-align: center;
  transition: transform 0.2s;
}

.feature-card:hover {
  transform: translateY(-2px);
}

.feature-icon {
  width: 48px;
  height: 48px;
  margin: 0 auto 20px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  background: var(--light-bg);
  border-radius: 12px;
  color: var(--accent);
}

.feature-card h3 {
  font-size: 17px;
  font-weight: 700;
  margin-bottom: 8px;
  letter-spacing: -0.2px;
}

.feature-card p {
  font-size: 14px;
  line-height: 1.43;
  color: #555555;
}

/* ========================================
   Feature Detail — Alternating
   ======================================== */

.feature-detail {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 80px;
  align-items: center;
}

.feature-detail--reverse {
  direction: rtl;
}

.feature-detail--reverse > * {
  direction: ltr;
}

.feature-detail-text h2 {
  margin-bottom: 16px;
}

.feature-detail-text p {
  font-size: 17px;
  line-height: 1.59;
}

.section--dark .feature-detail-text p {
  color: rgba(255, 255, 255, 0.75);
}

.feature-detail-text .accent-line {
  width: 40px;
  height: 3px;
  background: var(--accent);
  border-radius: 2px;
  margin-bottom: 24px;
}

/* ========================================
   Final CTA
   ======================================== */

.final-cta {
  text-align: center;
  padding: 120px 24px;
}

.final-cta h2 {
  margin-bottom: 12px;
}

.final-cta p {
  color: var(--text-secondary-light);
  margin-bottom: 40px;
  font-size: 17px;
}

/* ========================================
   Footer
   ======================================== */

.footer {
  padding: 64px 24px 32px;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 48px;
}

.footer-brand p {
  font-size: 14px;
  color: var(--text-secondary-dark);
  margin-top: 8px;
  line-height: 1.5;
}

.footer-col h4 {
  font-size: 12px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-secondary-dark);
  margin-bottom: 16px;
}

.footer-col ul {
  list-style: none;
}

.footer-col li {
  margin-bottom: 10px;
}

.footer-col a {
  font-size: 14px;
  color: rgba(255, 255, 255, 0.7);
  transition: color 0.2s;
}

.footer-col a:hover {
  color: var(--white);
  opacity: 1;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-bottom p {
  font-size: 12px;
  color: var(--text-secondary-dark);
}

.footer-bottom-links {
  display: flex;
  gap: 20px;
}

.footer-bottom-links a {
  font-size: 12px;
  color: var(--text-secondary-dark);
}

/* ========================================
   Responsive — Mobile First Overrides
   ======================================== */

@media (max-width: 768px) {
  :root {
    --section-padding: 80px 20px;
  }

  /* Nav mobile */
  .nav-links {
    display: none;
    position: absolute;
    top: 52px;
    left: 0;
    right: 0;
    background: rgba(28, 28, 30, 0.96);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    flex-direction: column;
    padding: 20px 24px;
    gap: 20px;
  }

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

  .nav-toggle {
    display: block;
  }

  /* Hero */
  .headline-hero {
    font-size: 36px;
    letter-spacing: -1px;
  }

  .hero {
    padding-top: 120px;
    padding-bottom: 60px;
    min-height: auto;
  }

  .hero-subtitle {
    font-size: 16px;
  }

  .hero-cta {
    flex-direction: column;
    align-items: center;
    gap: 12px;
    margin-bottom: 48px;
  }

  .screenshot-placeholder {
    max-width: 220px;
  }

  /* Features grid */
  .headline-section {
    font-size: 28px;
  }

  .features-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    margin-top: 40px;
  }

  .feature-card {
    padding: 24px 16px;
  }

  /* Feature detail */
  .feature-detail {
    grid-template-columns: 1fr;
    gap: 40px;
    text-align: center;
  }

  .feature-detail--reverse {
    direction: ltr;
  }

  .feature-detail-text .accent-line {
    margin: 0 auto 24px;
  }

  .screenshot-placeholder {
    max-width: 200px;
  }

  /* Footer */
  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 32px;
  }

  .footer-brand {
    grid-column: 1 / -1;
  }

  .footer-bottom {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }
}

@media (max-width: 480px) {
  .features-grid {
    grid-template-columns: 1fr;
  }

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