@import url('https://fonts.googleapis.com/css2?family=Noto+Serif+JP:wght@400;500;700&family=Noto+Sans+JP:wght@400;500&display=swap');

:root {
  --color-navy: #1a2744;
  --color-navy-light: #2c3e6b;
  --color-bg: #fafaf8;
  --color-bg-alt: #f2f1ee;
  --color-border: #d8d5cf;
  --color-text: #2d2d2d;
  --color-text-light: #5a5a5a;
  --color-text-muted: #8a8a8a;
  --color-accent: #3a5a8c;
  --color-accent-hover: #2c4570;
  --color-link: #3a5a8c;
  --font-serif: 'Noto Serif JP', 'Georgia', serif;
  --font-sans: 'Noto Sans JP', 'Helvetica Neue', sans-serif;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-serif);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.8;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ===== HEADER ===== */
#site-header {
  background: var(--color-navy);
  color: white;
  padding: 0;
  border-bottom: 3px solid var(--color-accent);
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem 1.5rem;
}

.header-math-decoration {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  color: rgba(255,255,255,0.35);
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}

#site-title {
  font-size: 2rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  line-height: 1.2;
}

#site-title a {
  color: white;
  text-decoration: none;
}

#site-title a:hover {
  color: rgba(255,255,255,0.85);
}

#site-subtitle {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: rgba(255,255,255,0.65);
  margin-top: 0.4rem;
  font-weight: 400;
}

/* ===== NAV ===== */
#site-nav {
  background: var(--color-navy-light);
  border-bottom: 1px solid rgba(255,255,255,0.1);
}

.nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 1.5rem;
  display: flex;
  align-items: center;
  gap: 0;
}

.nav-inner a {
  color: rgba(255,255,255,0.8);
  text-decoration: none;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  padding: 0.75rem 1rem;
  display: block;
  transition: color 0.2s, background 0.2s;
}

.nav-inner a:hover {
  color: white;
  background: rgba(255,255,255,0.08);
}

/* ===== MAIN LAYOUT ===== */
#main-wrapper {
  max-width: 1100px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
  display: grid;
  grid-template-columns: 1fr 280px;
  gap: 3rem;
  flex: 1;
}

#main-content {
  min-width: 0;
}

/* ===== SIDEBAR ===== */
#sidebar {
  min-width: 0;
}

.sidebar-widget {
  background: white;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 1.25rem;
  margin-bottom: 1.5rem;
}

.sidebar-widget h3 {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  border-bottom: 1px solid var(--color-border);
  padding-bottom: 0.5rem;
  margin-bottom: 0.75rem;
}

.sidebar-widget p {
  font-size: 0.9rem;
  color: var(--color-text-light);
  line-height: 1.6;
}

.sidebar-widget ul {
  list-style: none;
  font-size: 0.9rem;
}

.sidebar-widget ul li {
  padding: 0.25rem 0;
  border-bottom: 1px dotted var(--color-border);
}

.sidebar-widget ul li:last-child {
  border-bottom: none;
}

.sidebar-widget ul li a {
  color: var(--color-link);
  text-decoration: none;
}

.sidebar-widget ul li a:hover {
  text-decoration: underline;
}

.admin-link-widget {
  background: var(--color-bg-alt);
  border-color: #c0bdb6;
}

.admin-link-widget a {
  display: inline-block;
  color: var(--color-text-light);
  text-decoration: none;
  font-family: var(--font-sans);
  font-size: 0.85rem;
}

.admin-link-widget a:hover {
  color: var(--color-text);
  text-decoration: underline;
}

/* ===== PAGE TITLE ===== */
.page-section-title {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.15em;
  margin-bottom: 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--color-border);
}

/* ===== ARTICLE CARD (INDEX) ===== */
.article-list {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.article-card {
  position: relative;
  background: white;
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 1.25rem 1.5rem;
  margin-bottom: 1rem;
  transition: box-shadow 0.2s;
  cursor: pointer;
}

.article-card:hover {
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
}

.article-card.cursed {
}

.article-number {
  font-family: var(--font-sans);
  font-size: 0.7rem;
  color: var(--color-text-muted);
  margin-bottom: 0.2rem;
  letter-spacing: 0.05em;
}

.article-card-title {
  font-size: 1.05rem;
  font-weight: 500;
  margin-bottom: 0.4rem;
}

.article-card-title a {
  color: var(--color-text);
  text-decoration: none;
}

.article-card-title a::after {
  content: '';
  position: absolute;
  inset: 0;
}

.article-card-title a:hover {
  color: var(--color-accent);
}

.article-meta {
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--color-text-muted);
  display: flex;
  gap: 1rem;
  align-items: center;
  flex-wrap: wrap;
}

.article-excerpt {
  font-size: 0.9rem;
  color: var(--color-text-light);
  margin-top: 0.5rem;
  line-height: 1.6;
}

.tag-updated {
  display: inline-block;
  background: #e8edf5;
  color: var(--color-accent);
  font-size: 0.7rem;
  padding: 0.1rem 0.4rem;
  border-radius: 2px;
  font-family: var(--font-sans);
}

/* ===== ARTICLE PAGE ===== */
.article-page {
  max-width: 100%;
}

.article-header {
  margin-bottom: 2rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--color-border);
}

.article-no-badge {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  color: var(--color-text-muted);
  letter-spacing: 0.05em;
  margin-bottom: 0.5rem;
}

.article-title {
  font-size: 1.6rem;
  font-weight: 700;
  line-height: 1.4;
  color: var(--color-text);
  margin-bottom: 0.75rem;
}

.article-date-info {
  font-family: var(--font-sans);
  font-size: 0.82rem;
  color: var(--color-text-muted);
}

.article-date-info .updated {
  display: none;
}

.article-body {
  font-size: 1rem;
  line-height: 1.95;
  color: var(--color-text);
}

.article-body img {
  width: 100%;
  height: auto;
  display: block;
}

.article-body p {
  margin-bottom: 1.2em;
}

.article-body h2 {
  font-size: 1.2rem;
  margin: 2em 0 0.75em;
  padding-bottom: 0.3em;
  border-bottom: 1px solid var(--color-border);
}

.article-body h3 {
  font-size: 1.05rem;
  margin: 1.5em 0 0.5em;
  color: var(--color-navy-light);
}

.article-body .math-block {
  overflow-x: auto;
  padding: 1rem;
  background: var(--color-bg-alt);
  border-left: 3px solid var(--color-accent);
  margin: 1.5em 0;
  border-radius: 0 4px 4px 0;
}

.article-figure {
  margin: 1.5em auto;
  text-align: center;
}

.article-figure img {
  max-width: 100%;
  height: auto;
  border-radius: 4px;
}

.article-nav {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 2.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--color-border);
}

.article-nav a {
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--color-link);
  text-decoration: none;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--color-border);
  border-radius: 3px;
  transition: background 0.2s;
}

.article-nav a:hover {
  background: var(--color-bg-alt);
}

/* ===== CURSED ARTICLE ===== */
.cursed-body {
  font-family: monospace;
  font-size: 0.85rem;
  line-height: 1.5;
  color: #2a2a2a;
  word-break: break-all;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}

/* ===== FOOTER ===== */
#site-footer {
  background: var(--color-navy);
  color: rgba(255,255,255,0.5);
  text-align: center;
  padding: 1.5rem;
  font-family: var(--font-sans);
  font-size: 0.8rem;
  margin-top: auto;
}

#site-footer a {
  color: rgba(255,255,255,0.6);
  text-decoration: none;
}

/* ===== BACK LINK ===== */
.back-link {
  display: inline-block;
  margin-bottom: 1.5rem;
  font-family: var(--font-sans);
  font-size: 0.85rem;
  color: var(--color-link);
  text-decoration: none;
}

.back-link:hover {
  text-decoration: underline;
}

/* ===== ARTICLE PAGE FULL WIDTH LAYOUT ===== */
.single-column #main-wrapper {
  grid-template-columns: 1fr;
  max-width: 800px;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  #main-wrapper {
    grid-template-columns: 1fr;
    gap: 2rem;
    padding: 1rem;
  }

  #site-title {
    font-size: 1.5rem;
  }

  .article-title {
    font-size: 1.3rem;
  }

  .article-nav {
    flex-direction: column;
  }
}