/* ===== RESET & BASE ===== */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

:root {
  --bg:        #0a0c12;
  --bg-card:   #0f1220;
  --bg-card2:  #131726;
  --border:    rgba(99, 179, 237, 0.12);
  --accent:    #3b82f6;
  --accent-2:  #06b6d4;
  --glow:      rgba(59, 130, 246, 0.35);
  --text:      #e2e8f0;
  --text-muted:#64748b;
  --text-dim:  #94a3b8;
  --radius:    14px;
  --font:      'Inter', 'PingFang SC', 'Microsoft YaHei', system-ui, sans-serif;
}

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== HERO ===== */
.hero {
  position: relative;
  padding: 100px 0 80px;
  overflow: hidden;
  text-align: center;
}

.hero-bg {
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 70% 50% at 50% 0%, rgba(59,130,246,0.18) 0%, transparent 70%),
    radial-gradient(ellipse 40% 30% at 80% 60%, rgba(6,182,212,0.10) 0%, transparent 60%);
  pointer-events: none;
}

.hero-content { position: relative; z-index: 1; }

.badge {
  display: inline-block;
  padding: 4px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: 12px;
  letter-spacing: 0.08em;
  color: var(--accent-2);
  background: rgba(6,182,212,0.07);
  margin-bottom: 24px;
  text-transform: uppercase;
}

.logo-text {
  font-size: clamp(2.8rem, 7vw, 5rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  background: linear-gradient(135deg, #e2e8f0 30%, var(--accent) 70%, var(--accent-2) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
  margin-bottom: 20px;
}

.tagline-zh {
  font-size: 1.2rem;
  color: var(--text-dim);
  margin-bottom: 6px;
}

.tagline-en {
  font-size: 0.95rem;
  color: var(--text-muted);
}

/* ===== SECTIONS ===== */
.download-section,
.changelog-section {
  padding: 72px 0;
}

.changelog-section {
  background: linear-gradient(180deg, transparent, rgba(59,130,246,0.03) 50%, transparent);
}

.section-title {
  text-align: center;
  margin-bottom: 48px;
  font-size: 1.6rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.section-title .zh { display: block; color: var(--text); }
.section-title .en { display: block; font-size: 0.85rem; font-weight: 400; color: var(--text-muted); margin-top: 4px; letter-spacing: 0.04em; }

/* ===== PLATFORM GRID ===== */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 20px;
}

.platform-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 16px;
  transition: border-color 0.25s, box-shadow 0.25s;
}

.platform-card.active {
  border-color: rgba(59,130,246,0.35);
  box-shadow: 0 0 32px rgba(59,130,246,0.10), inset 0 1px 0 rgba(255,255,255,0.04);
}

.platform-card.active:hover {
  border-color: rgba(59,130,246,0.6);
  box-shadow: 0 0 48px var(--glow), inset 0 1px 0 rgba(255,255,255,0.06);
}

.platform-card.disabled {
  opacity: 0.45;
}

.platform-icon {
  width: 48px;
  height: 48px;
  color: var(--accent);
}

.platform-card.disabled .platform-icon { color: var(--text-muted); }

.platform-icon svg { width: 100%; height: 100%; }

.platform-info { text-align: center; }

.platform-name {
  display: block;
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 4px;
}

.platform-req {
  display: block;
  font-size: 0.78rem;
  color: var(--text-muted);
}

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 24px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  border: none;
  text-decoration: none;
  transition: background 0.2s, box-shadow 0.2s, transform 0.15s;
  white-space: nowrap;
}

.btn-icon { width: 16px; height: 16px; flex-shrink: 0; }

.btn-primary {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #fff;
  box-shadow: 0 4px 20px rgba(59,130,246,0.35);
}

.btn-primary:hover {
  box-shadow: 0 6px 28px rgba(59,130,246,0.55);
  transform: translateY(-1px);
}

.btn-primary:active { transform: translateY(0); }

.btn-disabled {
  background: rgba(255,255,255,0.06);
  color: var(--text-muted);
  cursor: not-allowed;
}

/* bilingual button text */
.btn .zh,
.btn .en {
  display: inline;
}

.file-meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.03em;
}

/* ===== CHANGELOG ===== */
.changelog-card {
  background: var(--bg-card2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 32px;
  max-width: 680px;
  margin: 0 auto;
}

.changelog-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
}

.version-tag {
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #fff;
  font-size: 0.8rem;
  font-weight: 700;
  padding: 3px 10px;
  border-radius: 6px;
  letter-spacing: 0.04em;
}

.release-date {
  font-size: 0.82rem;
  color: var(--text-muted);
}

.changelog-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.changelog-list li {
  display: flex;
  gap: 14px;
  align-items: flex-start;
}

.change-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  flex-shrink: 0;
  margin-top: 7px;
  box-shadow: 0 0 8px var(--accent);
}

.change-zh {
  font-size: 0.95rem;
  color: var(--text);
  margin-bottom: 3px;
}

.change-en {
  font-size: 0.82rem;
  color: var(--text-muted);
}

/* ===== FOOTER ===== */
.footer {
  border-top: 1px solid var(--border);
  padding: 28px 0;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 8px;
}

.footer-logo {
  font-weight: 700;
  font-size: 0.95rem;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.footer-copy {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 600px) {
  .hero { padding: 72px 0 56px; }
  .platform-grid { grid-template-columns: 1fr; }
  .changelog-card { padding: 22px 20px; }
  .footer-inner { justify-content: center; text-align: center; }
}

/* ===== TOPNAV ===== */
.topnav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(10, 12, 18, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.topnav-inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 52px;
}

.nav-logo {
  font-weight: 700;
  font-size: 1rem;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.lang-toggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 5px 14px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: rgba(255,255,255,0.04);
  color: var(--text-dim);
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: border-color 0.2s, color 0.2s, background 0.2s;
  letter-spacing: 0.04em;
}

.lang-toggle:hover {
  border-color: rgba(59,130,246,0.5);
  color: var(--accent);
  background: rgba(59,130,246,0.08);
}

.lang-icon { font-size: 0.9rem; }