/* XiaoXi Project Site - Dark Theme */
:root {
  --bg: #0a0e1a;
  --bg2: #0f172a;
  --card: rgba(15,23,42,0.6);
  --border: #1e293b;
  --cyan: #22d3ee;
  --green: #34d399;
  --purple: #a78bfa;
  --pink: #f472b6;
  --yellow: #fbbf24;
  --white: #e2e8f0;
  --gray: #94a3b8;
  --dark: #475569;
}

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

body {
  font-family: -apple-system, 'SF Pro', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--white);
  line-height: 1.7;
  min-height: 100vh;
}

/* Header / Nav */
nav {
  position: fixed;
  top: 0;
  width: 100%;
  background: rgba(10,14,26,0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  z-index: 100;
  padding: 0 2rem;
}

nav .inner {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 60px;
}

nav .logo {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--cyan);
  text-decoration: none;
}

nav .logo span { color: var(--white); }

nav .links { display: flex; gap: 2rem; }

nav .links a {
  color: var(--gray);
  text-decoration: none;
  font-size: 0.9rem;
  transition: color 0.2s;
}

nav .links a:hover { color: var(--cyan); }

/* Main content */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 2rem;
}

/* Hero Section */
.hero {
  padding-top: 140px;
  padding-bottom: 80px;
  text-align: center;
}

.hero h1 {
  font-size: 3rem;
  font-weight: 800;
  margin-bottom: 1rem;
}

.hero h1 .accent { color: var(--cyan); }

.hero .tagline {
  font-size: 1.2rem;
  color: var(--gray);
  margin-bottom: 2rem;
  max-width: 600px;
  margin-left: auto;
  margin-right: auto;
}

.hero .buttons {
  display: flex;
  gap: 1rem;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 0.7rem 1.8rem;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--cyan);
  color: var(--bg);
}

.btn-primary:hover {
  background: #06b6d4;
  transform: translateY(-2px);
}

.btn-outline {
  border: 1px solid var(--border);
  color: var(--white);
  background: transparent;
}

.btn-outline:hover {
  border-color: var(--cyan);
  color: var(--cyan);
}

/* Section */
section {
  padding: 80px 0;
}

section h2 {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 0.5rem;
}

section .subtitle {
  color: var(--gray);
  margin-bottom: 2rem;
}

/* Feature grid */
.features {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.feature-card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  transition: border-color 0.2s;
}

.feature-card:hover { border-color: var(--cyan); }

.feature-card .icon {
  font-size: 2rem;
  margin-bottom: 0.8rem;
}

.feature-card h3 {
  font-size: 1.1rem;
  margin-bottom: 0.5rem;
}

.feature-card p {
  color: var(--gray);
  font-size: 0.85rem;
}

/* Version cards */
.versions {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.5rem;
  margin-top: 2rem;
}

.vcard {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  position: relative;
  overflow: hidden;
}

.vcard::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
}

.vcard.pen::before { background: var(--cyan); }
.vcard.pen-eye::before { background: var(--pink); }
.vcard.desk::before { background: var(--purple); }
.vcard.desk-eye::before { background: var(--yellow); }

.vcard .tag {
  display: inline-block;
  padding: 0.15rem 0.6rem;
  border-radius: 999px;
  font-size: 0.7rem;
  font-weight: 600;
  margin-bottom: 0.8rem;
}

.vcard.pen .tag { background: rgba(34,211,238,0.15); color: var(--cyan); }
.vcard.pen-eye .tag { background: rgba(244,114,182,0.15); color: var(--pink); }
.vcard.desk .tag { background: rgba(167,139,250,0.15); color: var(--purple); }
.vcard.desk-eye .tag { background: rgba(251,191,36,0.15); color: var(--yellow); }

.vcard h3 { font-size: 1.1rem; margin-bottom: 0.3rem; }

.vcard .price {
  font-size: 1.5rem;
  font-weight: 700;
  margin: 0.5rem 0;
}

.vcard.pen .price { color: var(--cyan); }
.vcard.pen-eye .price { color: var(--pink); }
.vcard.desk .price { color: var(--purple); }
.vcard.desk-eye .price { color: var(--yellow); }

.vcard .cost {
  font-size: 0.75rem;
  color: var(--dark);
  margin-bottom: 0.8rem;
}

.vcard .feat-list { list-style: none; }
.vcard .feat-list li {
  font-size: 0.8rem;
  color: var(--gray);
  padding: 0.15rem 0;
}

.vcard .feat-list li .y { color: var(--green); }
.vcard .feat-list li .n { color: var(--dark); }

/* Mermaid diagrams */
.mermaid-wrap {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 2rem;
  overflow-x: auto;
  margin: 2rem 0;
}

/* Comparison table */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 2rem 0;
}

table th, table td {
  padding: 0.8rem 1rem;
  border-bottom: 1px solid var(--border);
  text-align: left;
  font-size: 0.85rem;
}

table th {
  color: var(--gray);
  font-weight: 500;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

table td.hl {
  color: var(--cyan);
  font-weight: 600;
}

/* BOM table */
.bom-table {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
  margin: 1rem 0;
  overflow-x: auto;
}

.bom-table table { margin: 0; }

/* Footer */
footer {
  border-top: 1px solid var(--border);
  padding: 3rem 0;
  text-align: center;
  color: var(--dark);
  font-size: 0.8rem;
}

footer a {
  color: var(--gray);
  text-decoration: none;
}

footer a:hover { color: var(--cyan); }

footer .links { margin-bottom: 1rem; }
footer .links a { margin: 0 1rem; }

/* Responsive */
@media (max-width: 768px) {
  .hero h1 { font-size: 2rem; }
  .hero .tagline { font-size: 1rem; }
  nav .links { gap: 1rem; }
  nav .links a { font-size: 0.8rem; }
  section { padding: 50px 0; }
  section h2 { font-size: 1.5rem; }
}

/* Language toggle button */
#lang-toggle {
  background: rgba(34,211,238,0.15);
  color: #22d3ee;
  border: 1px solid rgba(34,211,238,0.3);
  padding: 0.2rem 0.7rem;
  border-radius: 6px;
  font-size: 0.8rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  margin-left: 0.5rem;
}

#lang-toggle:hover {
  background: rgba(34,211,238,0.25);
  border-color: #22d3ee;
}