:root {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
}

body {
  margin: 0;
  min-height: 100svh;
  background: #0b0b0c;
  color: #f5f6f7;
  display: flex;
  flex-direction: column;
}

.topbar {
  padding: 1.1rem 1.75rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid rgba(255, 255, 255, .06);
}

.topbar .brand {
  font-weight: 600;
  letter-spacing: .3px;
  color: #f5f6f7;
  text-decoration: none;
  font-size: 1rem;
}

.topbar nav {
  display: flex;
  gap: 1.5rem;
}

.topbar nav a {
  color: #f5f6f7;
  text-decoration: none;
  opacity: .7;
  font-size: .95rem;
}

.topbar nav a:hover,
.topbar nav a.active {
  opacity: 1;
}

main {
  flex: 1;
  display: grid;
  place-items: center;
  padding: 2rem 1rem;
}

.card {
  padding: 2.5rem;
  border-radius: 1.25rem;
  background: #121316;
  box-shadow: 0 6px 24px rgba(0, 0, 0, .35);
  max-width: 720px;
  width: 100%;
  box-sizing: border-box;
}

h1 {
  margin: 0 0 .5rem;
  font-size: clamp(28px, 4vw, 40px);
  letter-spacing: .2px;
}

h2 {
  margin: 0 0 .5rem;
  font-size: clamp(22px, 3vw, 28px);
  letter-spacing: .2px;
}

p {
  line-height: 1.6;
  opacity: .9;
  margin: .5rem 0 0;
}

a {
  color: #9ad1ff;
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.muted {
  opacity: .65;
  font-size: .95rem;
  margin-top: 1rem;
}

.letter-list {
  list-style: none;
  padding: 0;
  margin: 1.75rem 0 0;
}

.letter-list li {
  padding: 1rem 0;
  border-bottom: 1px solid rgba(255, 255, 255, .06);
}

.letter-list li:first-child {
  padding-top: 0;
}

.letter-list li:last-child {
  border-bottom: none;
  padding-bottom: 0;
}

.letter-list .title {
  font-size: 1.05rem;
  color: #f5f6f7;
}

.letter-list .title:hover {
  color: #9ad1ff;
  text-decoration: none;
}

.letter-list .date {
  display: block;
  margin-top: .3rem;
  opacity: .55;
  font-size: .85rem;
}