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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans, "Noto Sans JP", sans-serif);
  background: var(--body-bg, #F8F5EF);
  color: var(--body-text, #1A1A2E);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

:root {
  --navy: #0D1F3C;
  --navy-mid: #162845;
  --navy-lite: #1E3560;
  --gold: #B8973E;
  --gold-lite: #D4AF55;
  --cream: #F8F5EF;
  --white: #FFFFFF;
  --text: #1A1A2E;
  --text-mid: #3D4466;
  --text-lite: #6B7399;
  --green: #2A6644;
  --green-bg: #EAF2ED;
  --blue: #1A4A7A;
  --blue-bg: #EBF1F8;
  --teal: #1A5F6A;
  --teal-bg: #E8F3F5;
  --radius-sm: 6px;
  --radius: 12px;
  --radius-lg: 20px;
  --shadow: 0 4px 24px rgba(13, 31, 60, 0.10);
  --shadow-lg: 0 12px 48px rgba(13, 31, 60, 0.18);
  --font-sans: 'Noto Sans JP', sans-serif;
  --font-serif: 'Noto Serif JP', serif;
  --body-bg: var(--cream);
  --body-text: var(--text);
}

.fade-up {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}
.fade-up.visible {
  opacity: 1;
  transform: none;
}
.fade-up:nth-child(2) {
  transition-delay: 0.08s;
}
.fade-up:nth-child(3) {
  transition-delay: 0.16s;
}
.fade-up:nth-child(4) {
  transition-delay: 0.24s;
}
.fade-up:nth-child(5) {
  transition-delay: 0.28s;
}
.fade-up:nth-child(6) {
  transition-delay: 0.35s;
}

@keyframes pulse {
  0%, 100% {
    opacity: 1;
    transform: scale(1);
  }
  50% {
    opacity: 0.5;
    transform: scale(0.8);
  }
}
@keyframes blink {
  0%, 100% {
    opacity: 1;
  }
  50% {
    opacity: 0.3;
  }
}
section {
  padding: 72px 32px;
}
@media (max-width: 640px) {
  section {
    padding: 52px 20px;
  }
}

.section-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.site-header {
  background: #fff;
  padding: 0 32px;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 4px rgba(0, 0, 0, 0.08);
  border-bottom: 1px solid #e5e5e5;
}
@media (max-width: 640px) {
  .site-header {
    padding: 0 20px;
  }
}

.header-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 64px;
}

.site-logo {
  display: flex;
  align-items: center;
  text-decoration: none;
}

.logo-img {
  height: 40px;
  width: auto;
  display: block;
  object-fit: contain;
}

.logo-company {
  font-size: 1.6rem;
  font-weight: 700;
  color: #333;
  margin-left: 10px;
}

.header-nav {
  display: flex;
  align-items: center;
  gap: 4px;
}
@media (max-width: 640px) {
  .header-nav {
    display: none;
  }
}
.header-nav a {
  color: #555;
  text-decoration: none;
  font-size: 0.82rem;
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  transition: all 0.2s;
  white-space: nowrap;
}
.header-nav a:hover {
  color: var(--navy);
  background: rgba(0, 0, 0, 0.04);
}
.header-nav .btn-contact {
  background: var(--navy);
  color: #fff;
  font-weight: 500;
  padding: 7px 16px;
}
.header-nav .btn-contact:hover {
  background: var(--navy-dark, #1a2a4a);
}

.hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  background: none;
  border: none;
  padding: 6px;
}
@media (max-width: 640px) {
  .hamburger {
    display: flex;
  }
}
.hamburger span {
  display: block;
  width: 24px;
  height: 2px;
  background: #555;
  border-radius: 2px;
  transition: all 0.3s;
}

.mobile-nav {
  display: none;
  position: fixed;
  top: 64px;
  left: 0;
  right: 0;
  bottom: 0;
  background: #fff;
  flex-direction: column;
  padding: 16px 24px;
  gap: 0;
  z-index: 99;
  overflow-y: auto;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}
.mobile-nav.open {
  display: flex;
}
.mobile-nav a {
  color: #333;
  text-decoration: none;
  font-size: 1rem;
  padding: 14px 16px;
  border-bottom: 1px solid #eee;
}
.mobile-nav a:hover {
  background: #f5f5f5;
}

.sub-nav {
  background: var(--navy);
  padding: 0 32px;
}
@media (max-width: 640px) {
  .sub-nav {
    padding: 0 16px;
  }
}

.sub-nav-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: 4px;
  height: 40px;
  overflow-x: auto;
}
.sub-nav-inner a {
  color: rgba(255, 255, 255, 0.8);
  text-decoration: none;
  font-size: 0.78rem;
  padding: 4px 12px;
  border-radius: var(--radius-sm);
  transition: all 0.2s;
  white-space: nowrap;
}
.sub-nav-inner a:hover {
  color: #fff;
  background: rgba(255, 255, 255, 0.12);
}

.site-footer {
  background: #060F1E;
  padding: 48px 32px 32px;
  color: rgba(255, 255, 255, 0.45);
}
@media (max-width: 640px) {
  .site-footer {
    padding: 36px 20px 24px;
  }
}

.footer-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.footer-top {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 48px;
  margin-bottom: 36px;
  padding-bottom: 36px;
  border-bottom: 1px solid rgba(255, 255, 255, 0.07);
  align-items: start;
}
@media (max-width: 640px) {
  .footer-top {
    grid-template-columns: 1fr;
    gap: 24px;
  }
}

.footer-logo-link {
  display: flex;
  align-items: center;
  text-decoration: none;
}

.footer-logo-img {
  height: 36px;
  width: auto;
}

.footer-company {
  font-size: 1.1rem;
  font-weight: 700;
  color: rgba(255, 255, 255, 0.85);
  margin-left: 10px;
}

.footer-tagline {
  font-size: 0.7rem;
  color: var(--gold-lite);
  margin-top: 6px;
}

.footer-desc {
  font-size: 0.78rem;
  line-height: 1.75;
  margin-top: 14px;
  max-width: 380px;
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 8px;
  align-items: flex-end;
}
@media (max-width: 640px) {
  .footer-links {
    align-items: flex-start;
  }
}
.footer-links a {
  font-size: 0.78rem;
  color: rgba(255, 255, 255, 0.45);
  text-decoration: none;
  transition: color 0.2s;
}
.footer-links a:hover {
  color: rgba(255, 255, 255, 0.8);
}

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.72rem;
  flex-wrap: wrap;
  gap: 8px;
}
.footer-bottom a {
  color: rgba(255, 255, 255, 0.35);
  text-decoration: none;
}
.footer-bottom a:hover {
  color: rgba(255, 255, 255, 0.65);
}

:root {
  --navy: #0B1E3A;
  --navy-mid: #142B52;
  --navy-lite: #1C3B6E;
  --gold: #B8973E;
  --gold-lite: #D4AF55;
  --gold-pale: #F7F0DC;
  --gold-soft: #EDE0B8;
  --cream: #FAFAF8;
  --warm-gray: #F4F2EE;
  --rule: #E2DDD4;
  --text: #1A1A2A;
  --text-mid: #42424F;
  --text-lite: #7A7A8A;
  --white: #FFFFFF;
  --red-accent: #C0392B;
  --r-sm: 6px;
  --r: 10px;
  --r-lg: 16px;
  --r-xl: 22px;
  --sh: 0 2px 16px rgba(11, 30, 58, 0.08);
  --sh-lg: 0 8px 40px rgba(11, 30, 58, 0.14);
}

.books-hero {
  background: linear-gradient(165deg, var(--navy) 0%, var(--navy-mid) 60%, var(--navy-lite) 100%);
  color: var(--white);
  padding: 80px 32px 56px;
  text-align: center;
}
@media (max-width: 640px) {
  .books-hero {
    padding: 64px 20px 40px;
  }
}

.books-hero-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.books-hero h1 {
  font-family: var(--font-serif);
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.5;
  margin-bottom: 12px;
}
@media (max-width: 640px) {
  .books-hero h1 {
    font-size: 1.5rem;
  }
}

.books-hero p {
  font-size: 0.88rem;
  color: rgba(255, 255, 255, 0.6);
  line-height: 1.7;
}

.filter-bar {
  background: var(--warm-gray);
  border-bottom: 1px solid var(--rule);
  padding: 0 32px;
  position: sticky;
  top: 0;
  z-index: 50;
}
@media (max-width: 640px) {
  .filter-bar {
    padding: 0 16px;
  }
}

.filter-bar-inner {
  max-width: 1100px;
  margin: 0 auto;
  display: flex;
  gap: 0;
  overflow-x: auto;
}

.filter-btn {
  background: none;
  border: none;
  padding: 14px 22px;
  font-family: var(--font-sans);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--text-lite);
  cursor: pointer;
  white-space: nowrap;
  border-bottom: 3px solid transparent;
  transition: color 0.2s, border-color 0.2s;
}
.filter-btn:hover {
  color: var(--text);
}
.filter-btn.active {
  color: var(--gold);
  border-bottom-color: var(--gold);
}

.filter-count {
  font-size: 0.7rem;
  font-weight: 400;
  color: var(--text-lite);
  margin-left: 4px;
}

.books-list-section {
  padding: 48px 32px 72px;
  background: var(--cream);
}
@media (max-width: 640px) {
  .books-list-section {
    padding: 32px 20px 56px;
  }
}

.books-list-inner {
  max-width: 1100px;
  margin: 0 auto;
}

.books-category-label {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 2px solid var(--gold);
  display: flex;
  align-items: center;
  gap: 8px;
}
.books-category-label .cat-icon {
  font-size: 1.2rem;
}

.books-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  margin-bottom: 48px;
}
@media (max-width: 900px) {
  .books-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}
@media (max-width: 640px) {
  .books-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
  }
}

.bk-card {
  background: var(--white);
  border: 1px solid var(--rule);
  border-radius: var(--r-lg);
  overflow: hidden;
  box-shadow: var(--sh);
  display: flex;
  flex-direction: column;
  text-decoration: none;
  color: inherit;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.bk-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 12px 48px rgba(0, 0, 0, 0.15);
}

.bk-card-img {
  background: linear-gradient(145deg, var(--warm-gray), #EAE8E2);
  padding: 20px 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 160px;
  position: relative;
}

.bk-cover {
  width: 90px;
  height: auto;
  border-radius: 3px;
  box-shadow: 4px 6px 16px rgba(0, 0, 0, 0.2);
}
@media (max-width: 640px) {
  .bk-cover {
    width: 70px;
  }
}

.bk-badge {
  position: absolute;
  top: 8px;
  left: 8px;
  background: var(--red-accent);
  color: var(--white);
  font-size: 0.58rem;
  font-weight: 700;
  padding: 2px 7px;
  border-radius: 3px;
  letter-spacing: 0.04em;
}

.bk-card-body {
  padding: 14px 16px 12px;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.bk-tag {
  display: inline-flex;
  align-items: center;
  font-size: 0.6rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  padding: 2px 8px;
  border-radius: 3px;
  width: fit-content;
}

.bk-tag-law {
  background: var(--gold-pale);
  color: var(--gold);
}

.bk-tag-exam {
  background: #EAF2ED;
  color: #2A6644;
}

.bk-title {
  font-family: var(--font-serif);
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--navy);
  line-height: 1.45;
}
@media (max-width: 640px) {
  .bk-title {
    font-size: 0.78rem;
  }
}

.bk-meta {
  font-size: 0.68rem;
  color: var(--text-lite);
  line-height: 1.5;
}

.bk-price {
  display: flex;
  align-items: baseline;
  gap: 3px;
  margin-top: auto;
  padding-top: 4px;
}

.bk-price-val {
  font-family: var(--font-serif);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--navy);
}

.bk-price-unit {
  font-size: 0.68rem;
  color: var(--text-lite);
}

.bk-card-foot {
  padding: 10px 16px 14px;
}

.bk-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--navy);
  color: var(--white);
  font-size: 0.74rem;
  font-weight: 700;
  padding: 9px 12px;
  border-radius: var(--r-sm);
  transition: background 0.2s;
}

.bk-card:hover .bk-btn {
  background: var(--navy-lite);
}

.books-empty {
  grid-column: 1/-1;
  text-align: center;
  padding: 48px 20px;
  color: var(--text-lite);
  font-size: 0.88rem;
}