:root {
  --bg: #f6f8fb;
  --text: #1f2937;
  --primary: #2563eb;
  --primary-dark: #1d4ed8;
  --card: #ffffff;
  --border: #dbe3f0;
  --muted: #64748b;
  --hero-start: #0b1220;
  --hero-end: #1e3a8a;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  background: radial-gradient(circle at top right, #eef4ff 0%, var(--bg) 45%);
  color: var(--text);
  line-height: 1.5;
}

.hero {
  background: linear-gradient(135deg, var(--hero-start), var(--hero-end));
  color: #fff;
  padding: 20px 24px 64px;
  position: relative;
  overflow: hidden;
}

.hero::after {
  content: "";
  position: absolute;
  right: -120px;
  top: -120px;
  width: 320px;
  height: 320px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(255, 255, 255, 0.2), rgba(255, 255, 255, 0));
  pointer-events: none;
}

.nav {
  max-width: 1080px;
  margin: 0 auto 34px;
  display: flex;
  gap: 16px;
  align-items: center;
  flex-wrap: wrap;
  padding: 10px 14px;
  border-radius: 14px;
  background: rgba(15, 23, 42, 0.22);
  border: 1px solid rgba(219, 234, 254, 0.14);
  backdrop-filter: blur(8px);
  position: relative;
  z-index: 1;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  letter-spacing: 0.2px;
  margin-right: auto;
}

.brand-logo {
  height: 30px;
  width: auto;
  display: block;
}

.nav-link {
  color: #dbeafe;
  text-decoration: none;
  padding: 6px 10px;
  border-radius: 8px;
  transition: all 0.2s ease;
}

.nav-link:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.12);
}

.lang-switch {
  display: inline-flex;
  gap: 6px;
}

.lang-btn {
  border: 1px solid rgba(219, 234, 254, 0.6);
  border-radius: 999px;
  padding: 5px 10px;
  background: rgba(255, 255, 255, 0.08);
  color: #dbeafe;
  cursor: pointer;
  transition: all 0.2s ease;
}

.lang-btn.active {
  background: #fff;
  color: #1d4ed8;
  border-color: #fff;
}

.hero-content {
  max-width: 1080px;
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.hero-content h1 {
  margin: 0 0 12px;
  font-size: clamp(1.6rem, 3vw, 2.4rem);
  letter-spacing: 0.3px;
}

.hero-content p {
  margin: 0 0 20px;
  max-width: 720px;
  line-height: 1.7;
  color: #e2e8f0;
}

.cta {
  display: inline-block;
  background: #fff;
  color: var(--primary-dark);
  text-decoration: none;
  border-radius: 999px;
  padding: 11px 18px;
  font-weight: 600;
  box-shadow: 0 8px 24px rgba(37, 99, 235, 0.28);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.cta:hover {
  transform: translateY(-1px);
  box-shadow: 0 10px 26px rgba(37, 99, 235, 0.35);
}

.container {
  max-width: 1080px;
  margin: 24px auto 36px;
  padding: 0 24px;
  display: grid;
  gap: 20px;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 22px;
  box-shadow: 0 12px 28px rgba(15, 23, 42, 0.07);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-2px);
  box-shadow: 0 14px 32px rgba(15, 23, 42, 0.1);
}

.card h2 {
  margin-top: 0;
  font-size: 1.25rem;
  margin-bottom: 14px;
}

.card ul {
  margin: 0;
  padding-left: 18px;
  line-height: 1.7;
}

details {
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px 14px;
  margin-bottom: 10px;
  background: #f8fbff;
}

summary {
  cursor: pointer;
  font-weight: 600;
}

details p {
  margin: 10px 0 0;
  line-height: 1.6;
}

.download-list {
  display: grid;
  gap: 10px;
}

.download-list a {
  color: var(--primary);
  text-decoration: none;
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 12px;
  background: #f9fbff;
}

.download-list a:hover {
  border-color: var(--primary);
}

form {
  display: grid;
  gap: 12px;
}

input,
textarea,
button {
  font: inherit;
}

input,
textarea {
  border: 1px solid #c8d3e4;
  border-radius: 10px;
  padding: 11px 12px;
  background: #fff;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

input:focus,
textarea:focus {
  outline: none;
  border-color: #93c5fd;
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

button {
  border: 0;
  border-radius: 10px;
  padding: 11px 14px;
  background: var(--primary);
  color: #fff;
  cursor: pointer;
  font-weight: 600;
  transition: all 0.2s ease;
}

button:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
}

button:disabled {
  opacity: 0.72;
  cursor: not-allowed;
  transform: none;
}

.form-message {
  margin: 0;
  min-height: 22px;
}

.form-helper {
  margin: -4px 0 0;
  color: var(--muted);
  font-size: 0.88rem;
}

.image-list {
  margin: 0;
  padding-left: 18px;
  color: #475569;
  font-size: 0.9rem;
}

.footer {
  text-align: center;
  font-size: 0.92rem;
  color: var(--muted);
  padding: 10px 20px 28px;
}

@media (max-width: 640px) {
  .hero {
    padding-left: 16px;
    padding-right: 16px;
    padding-bottom: 56px;
  }

  .nav {
    gap: 8px 10px;
    padding: 10px;
  }

  .brand-logo {
    height: 26px;
  }

  .container {
    padding: 0 16px;
    gap: 14px;
  }

  .card {
    padding: 16px;
  }
}