:root {
  --fg: #1a1a1a;
  --bg: #fafafa;
  --muted: #777;
  --border: #ddd;
  --popover-bg: #ffffff;
  --popover-border: #c7c7c7;
  --popover-shadow: 0 8px 32px rgba(0, 0, 0, 0.18);
}
@media (prefers-color-scheme: dark) {
  :root {
    --fg: #e8e8e8;
    --bg: #111;
    --muted: #888;
    --border: #2a2a2a;
    --popover-bg: #1c1c1c;
    --popover-border: #3a3a3a;
    --popover-shadow: 0 8px 32px rgba(0, 0, 0, 0.6);
  }
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", system-ui, sans-serif;
  line-height: 1.7;
  font-size: 18px;
}
header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1.2rem 1.5rem;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  gap: 1rem;
}
.brand {
  font-weight: 600;
  text-decoration: none;
  color: var(--fg);
  letter-spacing: -0.01em;
}
nav {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: 0.95rem;
}
nav a { color: var(--fg); }
.lang-form, .day-form { display: inline-flex; align-items: center; gap: 0.4rem; margin: 0; }
.lang-form select, .lang-form button,
.day-form select, .day-form button {
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.2rem 0.4rem;
  font: inherit;
  max-width: 14rem;
}
main {
  max-width: 36rem;
  margin: 2.5rem auto;
  padding: 0 1.5rem;
}
.intro {
  color: var(--muted);
  margin-bottom: 2rem;
  font-style: italic;
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
}
.info { position: relative; }
.info > summary {
  list-style: none;
  cursor: pointer;
  user-select: none;
  display: inline-block;
  font-style: normal;
  color: var(--muted);
  font-size: 1.05rem;
  line-height: 1;
}
.info > summary::-webkit-details-marker { display: none; }
.info > summary:hover { color: var(--fg); }
.info[open] .info-popover {
  position: absolute;
  top: 1.4rem;
  left: 0;
  background: var(--popover-bg);
  border: 1px solid var(--popover-border);
  border-radius: 8px;
  padding: 0.9rem 1.2rem;
  width: min(28rem, calc(100vw - 3rem));
  z-index: 10;
  font-style: normal;
  color: var(--fg);
  font-size: 0.95rem;
  line-height: 1.55;
  box-shadow: var(--popover-shadow);
}
.info-popover p { margin: 0 0 0.7rem 0; }
.info-popover p:last-child { margin-bottom: 0; }
.notice {
  color: var(--muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}
article h1 {
  font-size: 1.6rem;
  font-weight: 600;
  margin: 0 0 1.5rem 0;
  letter-spacing: -0.01em;
}
article p { margin: 0 0 1.1rem 0; }
footer {
  max-width: 36rem;
  margin: 3rem auto 2rem;
  padding: 0 1.5rem;
  color: var(--muted);
  font-size: 0.85rem;
}
@media (max-width: 480px) {
  body { font-size: 17px; }
  header { padding: 1rem; }
  main { margin: 1.5rem auto; }
}