:root {
  --color-bg: #ffffff;
  --color-text: #222222;
  --color-text-muted: #5a5a5a;
  --color-border: #e3e3e3;
  --color-accent: #2b5faa;
  --color-accent-dark: #1f4780;
  --color-surface: #f7f8fa;
  --max-width: 780px;
  --font-base: "Hiragino Kaku Gothic ProN", "Yu Gothic", "Meiryo", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #16181c;
    --color-text: #e8e8e8;
    --color-text-muted: #a3a3a3;
    --color-border: #30333a;
    --color-accent: #6fa3e0;
    --color-accent-dark: #8fb8e8;
    --color-surface: #1f2227;
  }
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-base);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.8;
  font-size: 16px;
  word-break: break-word;
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

a {
  color: var(--color-accent);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

/* Header */
.site-header {
  border-bottom: 1px solid var(--color-border);
  background: var(--color-surface);
}

.site-header-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 1rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

.site-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--color-text);
}
.site-title a {
  color: inherit;
}

.site-nav ul {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin: 0;
  padding: 0;
}

.site-nav a {
  color: var(--color-text-muted);
  font-size: 0.92rem;
}
.site-nav a:hover {
  color: var(--color-accent);
}

/* Layout */
main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 2rem 1.25rem 4rem;
}

/* Top page hero */
.hero {
  padding: 0 0 2rem;
  border-bottom: 1px solid var(--color-border);
  margin-bottom: 2rem;
  text-align: center;
}
.hero img {
  border-radius: 8px;
  margin: 0 auto 1.25rem;
}
.hero h1 {
  font-size: 1.6rem;
  margin: 0 0 0.5rem;
}
.hero p {
  color: var(--color-text-muted);
  margin: 0;
}

/* Feature blocks (infographics / character speech) on top page */
.feature-block {
  margin: 1.75rem 0;
}
.feature-block img {
  border-radius: 8px;
  margin: 0 auto;
}
.speech-wrap {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  margin: 1.75rem 0;
}
.speech-wrap img {
  width: 130px;
  flex-shrink: 0;
}
.speech-bubble {
  position: relative;
  background: var(--color-surface);
  border: 2px solid var(--color-accent);
  border-radius: 10px;
  padding: 0.9rem 1.1rem;
  font-weight: 700;
  font-size: 0.95rem;
  flex: 1;
}
@media (max-width: 480px) {
  .speech-wrap {
    flex-direction: column;
    text-align: center;
  }
}

/* Sticky article-list toggle (accordion-style dropdown) */
.sticky-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(135deg, var(--color-accent-dark), var(--color-accent));
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.2);
  margin-bottom: 2rem;
}
.sticky-btn {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  max-width: 960px;
  margin: 0 auto;
  padding: 0.9rem 1.25rem;
  background: none;
  border: none;
  color: #fff;
  font-size: 1rem;
  font-weight: 700;
  cursor: pointer;
  gap: 0.75rem;
  font-family: inherit;
}
.sticky-btn-left {
  display: flex;
  align-items: center;
  gap: 0.6rem;
}
.sticky-badge {
  background: rgba(255, 255, 255, 0.25);
  border: 1.5px solid rgba(255, 255, 255, 0.5);
  border-radius: 20px;
  font-size: 0.78rem;
  padding: 0.15rem 0.7rem;
  white-space: nowrap;
}
.sticky-arrow {
  font-size: 0.85rem;
  transition: transform 0.25s;
}
.sticky-nav.open .sticky-arrow {
  transform: rotate(180deg);
}
.sticky-dropdown {
  display: none;
  background: var(--color-surface);
  border-top: 2px solid rgba(255, 255, 255, 0.2);
  box-shadow: 0 6px 16px rgba(0, 0, 0, 0.18);
  max-height: 70vh;
  overflow-y: auto;
}
.sticky-nav.open .sticky-dropdown {
  display: block;
}
.sticky-dropdown-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 0.5rem 1rem 0.75rem;
}
.article-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.article-list li {
  border-bottom: 1px solid var(--color-border);
}
.article-list li:last-child {
  border-bottom: none;
}
.article-list a {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  padding: 0.85rem 0.5rem;
  color: var(--color-text);
  font-size: 0.92rem;
  font-weight: 600;
}
.article-list a:hover {
  color: var(--color-accent);
  text-decoration: none;
}
.article-list .dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--color-accent);
  flex-shrink: 0;
}
.article-list .arrow {
  margin-left: auto;
  color: var(--color-text-muted);
  font-size: 0.8rem;
  flex-shrink: 0;
}
.article-list .soon {
  color: var(--color-text-muted);
  font-weight: 400;
  cursor: default;
}

/* Article page */
.article-header {
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 1.25rem;
}
.article-header h1 {
  font-size: 1.5rem;
  line-height: 1.5;
  margin: 0 0 0.5rem;
}
.article-meta {
  color: var(--color-text-muted);
  font-size: 0.85rem;
}

.article-body h2 {
  font-size: 1.25rem;
  margin: 2rem 0 0.75rem;
  padding-bottom: 0.4rem;
  border-bottom: 2px solid var(--color-accent);
}
.article-body h3 {
  font-size: 1.1rem;
  margin: 1.5rem 0 0.6rem;
}
.article-body p {
  margin: 0 0 1.1rem;
}
.article-body figure {
  margin: 1.25rem 0;
}
.article-body figcaption {
  font-size: 0.82rem;
  color: var(--color-text-muted);
  margin-top: 0.4rem;
}
.article-body ul,
.article-body ol {
  margin: 0 0 1.1rem;
  padding-left: 1.4rem;
}
.article-body blockquote {
  margin: 1.25rem 0;
  padding: 0.75rem 1rem;
  border-left: 4px solid var(--color-border);
  background: var(--color-surface);
  color: var(--color-text-muted);
}
.source-note {
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  background: var(--color-surface);
  margin-top: 2rem;
}
.site-footer-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 1.5rem 1.25rem;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}
.site-footer nav ul {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.9rem;
  margin: 0;
  padding: 0;
}
.site-footer nav a {
  color: var(--color-text-muted);
}

@media (max-width: 480px) {
  .site-header-inner {
    flex-direction: column;
    align-items: flex-start;
  }
}

/* Link cards (関連リンク・SNS) */
.link-card-list {
  display: grid;
  gap: 0.9rem;
  margin: 1.25rem 0;
}
.link-card {
  display: block;
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-dark));
  color: #fff;
  text-decoration: none;
  border-radius: 8px;
  padding: 1rem 1.25rem;
  font-weight: 700;
  font-size: 1.02rem;
  text-align: center;
  transition: opacity 0.2s, transform 0.15s;
}
.link-card:hover {
  opacity: 0.88;
  transform: translateY(-2px);
  text-decoration: none;
}
.link-card .link-url {
  display: block;
  font-size: 0.78rem;
  font-weight: 400;
  opacity: 0.85;
  margin-top: 0.3rem;
  word-break: break-all;
}
.link-card-x {
  background: linear-gradient(135deg, #1a1a1a, #333);
}
.link-card-youtube {
  background: linear-gradient(135deg, #d32f2f, #8f1616);
}
.link-card-sister {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-dark));
}