:root {
  --bg: #f7f3e9;
  --ink: #121212;
  --cobalt: #2b4bff;
  --yellow: #ffd53f;
  --mint: #c9f2d8;
  --card-bg: #ffffff;
  --border: 2px solid #121212;
  --shadow: 4px 4px 0 #121212;
  --font-main: 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-mono: 'Courier New', monospace;
}

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

body {
  background-color: var(--bg);
  color: var(--ink);
  font-family: var(--font-main);
  -webkit-font-smoothing: antialiased;
  padding-bottom: 80px; /* Space for mobile nav */
  overflow-x: hidden;
}

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

a {
  text-decoration: none;
  color: inherit;
}

h1, h2, h3 {
  line-height: 1.2;
}

/* Typography & Common */
.section-title {
  font-size: 1.8rem;
  font-weight: 800;
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 10px;
}
.section-title span {
  font-family: var(--font-mono);
  background: var(--yellow);
  font-size: 0.9rem;
  padding: 4px 8px;
  border: var(--border);
  border-radius: 4px;
}

.btn {
  display: inline-block;
  background: var(--cobalt);
  color: #fff;
  padding: 12px 24px;
  border-radius: 8px;
  font-weight: bold;
  font-size: 1.1rem;
  border: var(--border);
  box-shadow: var(--shadow);
  transition: transform 0.1s, box-shadow 0.1s;
  text-align: center;
}
.btn:active {
  transform: translate(2px, 2px);
  box-shadow: 2px 2px 0 #121212;
}

/* Layout */
.container {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 20px;
}

/* Sections */
section {
  padding: 60px 0;
  border-bottom: 2px dashed rgba(18,18,18,0.2);
}
section:last-of-type {
  border-bottom: none;
}

/* 01 Hero Feed */
.hero-feed {
  padding-top: 30px;
  text-align: center;
}
.video-card {
  background: #000;
  border-radius: 24px;
  overflow: hidden;
  border: var(--border);
  box-shadow: 6px 6px 0 rgba(43, 75, 255, 0.4);
  max-width: 380px;
  margin: 0 auto 30px;
  position: relative;
}
.video-card img {
  width: 100%;
  aspect-ratio: 9/16;
}
.hero-content h1 {
  font-size: 2.5rem;
  margin-bottom: 15px;
  letter-spacing: -1px;
}
.hero-content p {
  font-size: 1.1rem;
  margin-bottom: 30px;
  color: #444;
}
.download-btn-top {
  margin-bottom: 15px;
}

/* 02 Steps */
.steps-wrap {
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.step-item {
  background: var(--card-bg);
  border: var(--border);
  box-shadow: var(--shadow);
  padding: 20px;
  border-radius: 12px;
  display: flex;
  align-items: flex-start;
  gap: 20px;
}
.step-num {
  font-family: var(--font-mono);
  font-size: 2rem;
  font-weight: bold;
  color: var(--cobalt);
  background: var(--mint);
  padding: 10px;
  border-radius: 50%;
  width: 60px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}
.step-text h3 {
  font-size: 1.2rem;
  margin-bottom: 5px;
}
.step-text p {
  color: #555;
  font-size: 0.95rem;
}

/* 03 Complete List */
.split-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 30px;
  align-items: center;
}
.split-img {
  border: var(--border);
  border-radius: 16px;
  box-shadow: var(--shadow);
  overflow: hidden;
}
.split-img img {
  width: 100%;
  aspect-ratio: 16/9;
}
.split-text h2 {
  font-size: 2rem;
  margin-bottom: 15px;
}
.split-text ul {
  list-style: none;
  margin-top: 20px;
}
.split-text ul li {
  margin-bottom: 10px;
  padding-left: 20px;
  position: relative;
  font-weight: bold;
}
.split-text ul li::before {
  content: '✔';
  position: absolute;
  left: 0;
  color: var(--cobalt);
}

/* 04 Collection */
.grid-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}
.card-video {
  background: var(--card-bg);
  border: var(--border);
  border-radius: 16px;
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: transform 0.2s;
}
.card-video:hover {
  transform: translateY(-5px);
}
.card-video img {
  width: 100%;
  aspect-ratio: 16/9;
  border-bottom: var(--border);
}
.card-video-body {
  padding: 15px;
}
.card-video-body h3 {
  font-size: 1.1rem;
  margin-bottom: 8px;
}
.card-video-body p {
  font-size: 0.9rem;
  color: #666;
}

/* 05 Stats */
.stats-banner {
  background: var(--cobalt);
  color: #fff;
  border: var(--border);
  border-radius: 20px;
  overflow: hidden;
  border-radius: 20px;
  box-shadow: var(--shadow);
}
.stats-img {
  width: 100%;
  aspect-ratio: 16/9;
  border-bottom: var(--border);
}
.stats-data {
  padding: 30px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  text-align: center;
}
.stat-item h3 {
  font-size: 2.5rem;
  font-family: var(--font-mono);
  color: var(--yellow);
}
.stat-item p {
  font-size: 1rem;
  margin-top: 5px;
}

/* 06 Comments */
.comments-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}
.comment-card {
  background: var(--card-bg);
  border: var(--border);
  padding: 20px;
  border-radius: 12px;
  box-shadow: 4px 4px 0 var(--mint);
}
.comment-head {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 10px;
}
.avatar {
  width: 40px;
  height: 40px;
  background: var(--yellow);
  border: var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
}
.comment-name {
  font-weight: bold;
}
.comment-text {
  font-size: 1rem;
  line-height: 1.5;
}

/* 07 FAQ */
.faq-list {
  display: flex;
  flex-direction: column;
  gap: 15px;
}
details {
  background: var(--card-bg);
  border: var(--border);
  border-radius: 12px;
  padding: 15px;
  box-shadow: 2px 2px 0 #121212;
}
summary {
  font-weight: bold;
  font-size: 1.1rem;
  cursor: pointer;
  list-style: none;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
summary::after {
  content: '+';
  font-family: var(--font-mono);
  font-size: 1.5rem;
}
details[open] summary::after {
  content: '-';
}
details p {
  margin-top: 10px;
  color: #555;
  line-height: 1.6;
}

/* 08 Download CTA */
.download-section {
  text-align: center;
  background: var(--yellow);
  border: var(--border);
  border-radius: 24px;
  padding: 50px 20px;
  box-shadow: var(--shadow);
  margin-bottom: 40px;
}
.download-section h2 {
  font-size: 2rem;
  margin-bottom: 15px;
}
.download-section p {
  font-size: 1.1rem;
  margin-bottom: 30px;
  color: #222;
}
.btn-large {
  font-size: 1.3rem;
  padding: 15px 40px;
  background: var(--cobalt);
}

/* Footer */
footer {
  text-align: center;
  padding: 30px 20px;
  font-size: 0.8rem;
  color: #888;
}
footer p {
  margin-bottom: 8px;
}
footer a {
  color: #888;
  text-decoration: underline;
}
footer time {
  font-family: var(--font-mono);
}

/* Right Side Nav (Desktop) */
.side-nav {
  position: fixed;
  right: 20px;
  top: 50%;
  transform: translateY(-50%);
  display: none;
  flex-direction: column;
  gap: 15px;
  z-index: 100;
}
.nav-circle {
  width: 54px;
  height: 54px;
  border-radius: 50%;
  background: #fff;
  border: 2px solid #121212;
  box-shadow: 3px 3px 0 var(--cobalt);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: bold;
  font-size: 0.85rem;
  writing-mode: vertical-rl;
  text-orientation: upright;
  letter-spacing: 2px;
  transition: all 0.2s;
}
.nav-circle:hover {
  background: var(--yellow);
  transform: translateX(-3px);
}

/* Mobile Nav (Bottom Tab) */
.mobile-nav {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  background: #fff;
  border-top: 2px solid #121212;
  display: flex;
  justify-content: space-around;
  padding: 10px 0;
  z-index: 100;
  overflow-x: auto;
}
.mobile-nav::-webkit-scrollbar {
  display: none;
}
.mobile-nav a {
  font-size: 0.8rem;
  font-weight: bold;
  color: #121212;
  padding: 5px 8px;
  white-space: nowrap;
}
.mobile-nav a.active {
  color: var(--cobalt);
}

/* Media Queries */
@media (min-width: 768px) {
  .hero-feed {
    display: flex;
    flex-direction: column;
    align-items: center;
    padding-top: 60px;
  }
  .video-card {
    max-width: 450px;
  }
  .split-grid {
    grid-template-columns: 1fr 1fr;
  }
  .grid-cards {
    grid-template-columns: repeat(2, 1fr);
  }
  .comments-grid {
    grid-template-columns: repeat(3, 1fr);
  }
  .steps-wrap {
    flex-direction: row;
  }
  .step-item {
    flex: 1;
    flex-direction: column;
    align-items: center;
    text-align: center;
  }
  .step-text {
    margin-top: 15px;
  }
}

@media (min-width: 1024px) {
  .side-nav {
    display: flex;
  }
  .mobile-nav {
    display: none;
  }
  .grid-cards {
    grid-template-columns: repeat(3, 1fr);
  }
  .stats-data {
    padding: 40px;
    gap: 40px;
  }
  .stat-item h3 {
    font-size: 3.5rem;
  }
}