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

body {
  font-family: 'Segoe UI', system-ui, sans-serif;
  background: #0d1117;
  color: #e6edf3;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 3rem 1.5rem;
}

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

.badge a:hover {
  text-decoration: underline;
}

.badge {
  font-size: 0.75rem;
  color: #58a6ff;
  border: 1px solid #1f6feb66;
  background: #388bfd1a;
  padding: 0.3rem 0.8rem;
  border-radius: 999px;
  margin-bottom: 1.2rem;
}

h1 { font-size: 2.2rem; margin-bottom: 0.6rem; }

.subtitle {
  color: #8b949e;
  max-width: 640px;
  text-align: center;
  line-height: 1.6;
  margin-bottom: 2.5rem;
}
.subtitle strong { color: #c9d1d9; font-weight: 600; }
.subtitle a { color: #58a6ff; text-decoration: none; }
.subtitle a:hover { text-decoration: underline; }

.meta {
  display: grid;
  grid-template-columns: auto 1fr;
  column-gap: 1rem;
  row-gap: 0.45rem;
  margin: -1.6rem 0 2.4rem;
  font-size: 0.82rem;
}
.meta dt {
  color: #8b949e;
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.07em;
  font-weight: 600;
  text-align: right;
  padding-top: 0.12rem;
  white-space: nowrap;
}
.meta dd { display: flex; flex-wrap: wrap; gap: 0.3rem 1rem; }
.meta a { color: #58a6ff; text-decoration: none; }
.meta a:hover { text-decoration: underline; }

@media (max-width: 520px) {
  .meta { grid-template-columns: 1fr; row-gap: 0.15rem; }
  .meta dt { text-align: left; margin-top: 0.6rem; }
}

h2 {
  font-size: 1.05rem;
  color: #8b949e;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin: 2.5rem 0 1.2rem;
}

.cards {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1rem;
  width: 100%;
  max-width: 720px;
}
.card { flex: 0 1 330px; }
.card {
  background: #161b22;
  border: 1px solid #30363d;
  border-top: 2px solid #58a6ff;
  border-radius: 12px;
  padding: 1.2rem;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s, transform 0.15s;
}
.card:hover { border-color: #58a6ff; transform: translateY(-2px); }
.card-title { font-size: 0.95rem; font-weight: 600; margin-bottom: 0.3rem; }
.card-desc { font-size: 0.8rem; color: #8b949e; line-height: 1.5; }

.card.disabled { opacity: 0.5; cursor: not-allowed; border-top-color: #30363d; }
.card.disabled:hover { border-color: #30363d; transform: none; }
.in-progress {
  font-size: 0.62rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: #8b949e;
  border: 1px solid #6e768155;
  background: #6e76811a;
  border-radius: 999px;
  padding: 0.1rem 0.45rem;
  margin-left: 0.4rem;
  vertical-align: middle;
}

.note {
  max-width: 720px;
  width: 100%;
  margin-top: 1rem;
  padding: 0.9rem 1.1rem;
  font-size: 0.8rem;
  line-height: 1.6;
  color: #8b949e;
  background: #161b22;
  border: 1px solid #30363d;
  border-left: 2px solid #58a6ff;
  border-radius: 8px;
}
.note strong { color: #c9d1d9; }

.letter { max-width: 720px; width: 100%; }
.letter p {
  font-size: 0.92rem;
  line-height: 1.75;
  color: #c9d1d9;
  margin-bottom: 1.3rem;
}
.letter-links {
  max-width: 720px;
  width: 100%;
  margin-top: 0.6rem;
  font-size: 0.82rem;
}
.letter-links a {
  color: #58a6ff;
  text-decoration: none;
  margin-right: 1rem;
  white-space: nowrap;
}
.letter-links a:hover { text-decoration: underline; }

footer {
  margin-top: 3.5rem;
  font-size: 0.75rem;
  color: #484f58;
  text-align: center;
}
footer a { color: #58a6ff; text-decoration: none; margin-left: 0.5rem; }