:root {
  /* 深色主题 (默认) */
  --bg-color: #0A0A0A;
  --text-color: #FAFAFA;
  --text-secondary: rgba(250, 250, 250, 0.7);
  --nav-bg: rgba(10, 10, 10, 0.5);
  --line-color: #FAFAFA;
  --footer-color: #888888;
  --transition-speed: 0.6s;
  --font-main: "HarmonyOS Sans", "Source Han Sans CN", "PingFang SC", "Microsoft YaHei", sans-serif;
}

[data-theme="light"] {
  --bg-color: #FAFAFA;
  --text-color: #0A0A0A;
  --text-secondary: rgba(10, 10, 10, 0.7);
  --nav-bg: rgba(250, 250, 250, 0.5);
  --line-color: #0A0A0A;
}

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

html, body {
  width: 100%;
  height: 100%;
  font-family: var(--font-main);
  background-color: var(--bg-color);
  color: var(--text-color);
  transition: background-color var(--transition-speed), color var(--transition-speed);
  overflow-x: hidden;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

/* --- Navigation --- */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  padding: 2rem 4rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 1000;
  background: transparent;
  transition: background-color 0.3s ease;
}

.nav-links {
  display: flex;
  gap: 3rem;
  list-style: none;
}

.nav-item {
  position: relative;
  text-decoration: none;
  color: var(--text-color);
  font-size: 0.9rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  padding-bottom: 5px;
  cursor: pointer;
  transition: color 0.3s ease;
}

.nav-item::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 1px;
  background-color: var(--line-color);
  transition: width 0.3s ease;
}

.nav-item:hover::after {
  width: 100%;
}

.theme-toggle {
  background: none;
  border: 1px solid var(--text-color);
  color: var(--text-color);
  padding: 0.5rem 1rem;
  border-radius: 20px;
  cursor: pointer;
  font-size: 0.8rem;
  transition: all 0.3s ease;
}

.theme-toggle:hover {
  background: var(--text-color);
  color: var(--bg-color);
}

/* Mobile Nav Button (Hidden on Desktop) */
.mobile-menu-btn {
  display: none;
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 50px;
  height: 50px;
  background-color: var(--text-color);
  border-radius: 50%;
  z-index: 1001;
  border: none;
  cursor: pointer;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
  transition: transform 0.3s ease;
}

.mobile-menu-btn span {
  display: block;
  width: 20px;
  height: 2px;
  background-color: var(--bg-color);
  margin: 4px auto;
  transition: all 0.3s ease;
}

.mobile-menu-btn:hover {
  transform: scale(1.1);
}

/* --- Layout Sections --- */
.section {
  position: relative;
  width: 100%;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
  overflow: hidden;
}

/* Hero Section */
.hero {
  height: 100vh;
  position: relative;
}

.hero-bg {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 120%; /* For parallax */
  object-fit: cover;
  z-index: -1;
  transform: translateZ(-1px) scale(1.5); /* Hardware accel & base parallax setup */
  will-change: transform;
}

.hero-overlay {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.2); /* Slight dim for legibility */
}

.hero-content {
  text-align: center;
  z-index: 1;
  mix-blend-mode: difference; /* Ensure text visible on any bg */
  color: #fff; /* Always white due to difference blend */
}

.hero-title {
  font-size: 3rem;
  font-weight: 300;
  letter-spacing: 0.2em;
  margin-bottom: 1rem;
  opacity: 0;
  animation: fadeUp 1s ease 0.5s forwards;
}

/* Scroll Indicator */
.scroll-indicator {
  position: absolute;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%);
  animation: bounce 2s infinite;
  opacity: 0.8;
  cursor: pointer;
}

.scroll-arrow {
  width: 20px;
  height: 20px;
  border-right: 1px solid #fff;
  border-bottom: 1px solid #fff;
  transform: rotate(45deg);
}

/* --- Content Sections --- */
.content-block {
  padding: 8rem 4rem;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 4rem;
  align-items: center;
  max-width: 1600px;
  margin: 0 auto;
}

.content-block.reverse {
  direction: rtl;
}

.content-block.reverse .text-wrapper {
  direction: ltr;
}

.img-wrapper {
  position: relative;
  overflow: hidden;
  width: 100%;
  height: 80vh;
}

.content-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.6s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

.img-wrapper:hover .content-img {
  transform: scale(1.03);
}

.text-wrapper {
  padding: 0 2rem;
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.8s ease, transform 0.8s ease;
}

.text-wrapper.visible {
  opacity: 1;
  transform: translateY(0);
}

.section-title {
  font-size: 2rem;
  font-weight: 300;
  margin-bottom: 2rem;
  letter-spacing: 0.1em;
}

.section-desc {
  font-size: 1.1rem;
  line-height: 1.8;
  color: var(--text-secondary);
  font-weight: 300;
  text-align: justify;
}

/* --- Page Transitions --- */
.page-transition-overlay {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--bg-color);
  z-index: 9999;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.6s ease;
}

.page-transition-overlay.active {
  opacity: 1;
  pointer-events: all;
}

/* --- Footer --- */
.footer {
  padding: 2rem;
  text-align: center;
  font-size: 12px;
  color: var(--footer-color);
  background-color: var(--bg-color);
  border-top: 1px solid rgba(136, 136, 136, 0.1);
}

/* --- Navigation Hints --- */
.nav-hint {
  position: relative;
  width: 100%;
  padding: 4rem 0;
  text-align: center;
  cursor: pointer;
  transition: opacity 0.3s;
}

.nav-hint:hover {
  opacity: 0.7;
}

.nav-hint-text {
  font-size: 1.2rem;
  letter-spacing: 0.1em;
  text-decoration: none;
  color: var(--text-color);
  display: inline-block;
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s;
}

.nav-hint:hover .nav-hint-text {
  border-color: var(--line-color);
}

.fixed-hint {
  position: fixed;
  bottom: 2rem;
  font-size: 0.9rem;
  letter-spacing: 0.1em;
  color: var(--text-color);
  text-decoration: none;
  opacity: 0.6;
  transition: opacity 0.3s;
  z-index: 100;
}

.fixed-hint:hover {
  opacity: 1;
}

.hint-left { left: 2rem; writing-mode: vertical-rl; transform: rotate(180deg); }
.hint-right { right: 2rem; }

/* --- Animations --- */
@keyframes fadeUp {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes bounce {
  0%, 20%, 50%, 80%, 100% { transform: translate(-50%, 0); }
  40% { transform: translate(-50%, 10px); }
  60% { transform: translate(-50%, 5px); }
}

/* --- Responsive --- */
@media (max-width: 1024px) {
  .navbar {
    padding: 1.5rem 2rem;
  }
  
  .content-block {
    grid-template-columns: 1fr;
    padding: 4rem 2rem;
    gap: 2rem;
  }
  
  .content-block.reverse {
    direction: ltr;
  }

  .img-wrapper {
    height: 60vh;
  }
}

@media (max-width: 768px) {
  /* Mobile Nav */
  .nav-links {
    position: fixed;
    top: 0;
    right: -100%;
    width: 70%;
    height: 100vh;
    background-color: var(--bg-color);
    flex-direction: column;
    justify-content: center;
    padding: 2rem;
    transition: right 0.4s ease;
    box-shadow: -5px 0 15px rgba(0,0,0,0.1);
  }

  .nav-links.active {
    right: 0;
  }

  .mobile-menu-btn {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
  }

  .hero-title {
    font-size: 2rem;
  }

  .fixed-hint {
    display: none; /* Hide side hints on mobile */
  }

  .text-wrapper {
    padding: 0;
  }
}