/* ==========================================================================
   K10 Books — Global Stylesheet
   Pure static site. Zero remote fonts/CDNs. System font stack only.
   ========================================================================== */

/* --------------------------------------------------------------------------
   Design Tokens
   -------------------------------------------------------------------------- */
:root {
  /* Brand palette */
  --color-brand: #1f4e79;          /* deep publisher blue */
  --color-brand-dark: #163a5c;
  --color-brand-light: #3a72a6;
  --color-accent: #e0723a;         /* warm orange accent */
  --color-accent-dark: #c15a26;

  /* Neutrals */
  --color-ink: #1c2733;
  --color-ink-soft: #4a5a6a;
  --color-muted: #7a8894;
  --color-line: #e2e8ee;
  --color-bg: #ffffff;
  --color-bg-alt: #f5f8fb;
  --color-bg-dark: #12212f;

  /* Feedback */
  --color-success: #2e7d5b;
  --color-success-bg: #e6f4ec;

  /* Typography — system stack, nothing fetched remotely */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica,
    Arial, "Apple Color Emoji", "Segoe UI Emoji", sans-serif;
  --font-serif: Georgia, "Times New Roman", Times, serif;

  /* Type scale */
  --fs-xs: 0.78rem;
  --fs-sm: 0.88rem;
  --fs-base: 1rem;
  --fs-md: 1.15rem;
  --fs-lg: 1.4rem;
  --fs-xl: 1.9rem;
  --fs-2xl: 2.6rem;
  --fs-3xl: 3.2rem;

  /* Spacing scale */
  --sp-1: 0.25rem;
  --sp-2: 0.5rem;
  --sp-3: 0.75rem;
  --sp-4: 1rem;
  --sp-5: 1.5rem;
  --sp-6: 2rem;
  --sp-7: 3rem;
  --sp-8: 4rem;
  --sp-9: 6rem;

  /* Radii & shadows */
  --radius-sm: 4px;
  --radius: 8px;
  --radius-lg: 14px;
  --radius-pill: 999px;
  --shadow-sm: 0 1px 3px rgba(18, 33, 47, 0.08);
  --shadow: 0 4px 14px rgba(18, 33, 47, 0.10);
  --shadow-lg: 0 12px 34px rgba(18, 33, 47, 0.16);

  /* Layout */
  --container: 1160px;
  --container-narrow: 760px;
  --header-h: 68px;

  /* Motion */
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
  --dur: 0.22s;
}

/* --------------------------------------------------------------------------
   Reset / base
   -------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--fs-base);
  line-height: 1.6;
  color: var(--color-ink);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

a {
  color: var(--color-brand);
  text-decoration: none;
  transition: color var(--dur) var(--ease);
}

a:hover {
  color: var(--color-accent);
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-serif);
  line-height: 1.2;
  color: var(--color-ink);
  margin: 0 0 var(--sp-4);
}

h1 { font-size: var(--fs-2xl); }
h2 { font-size: var(--fs-xl); }
h3 { font-size: var(--fs-lg); }
h4 { font-size: var(--fs-md); }

p {
  margin: 0 0 var(--sp-4);
}

ul,
ol {
  margin: 0 0 var(--sp-4);
  padding-left: var(--sp-5);
}

hr {
  border: none;
  border-top: 1px solid var(--color-line);
  margin: var(--sp-6) 0;
}

/* --------------------------------------------------------------------------
   Layout helpers
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--sp-5);
}

.container--narrow {
  max-width: var(--container-narrow);
}

.section {
  padding: var(--sp-8) 0;
}

.section--alt {
  background: var(--color-bg-alt);
}

.section__head {
  text-align: center;
  max-width: 640px;
  margin: 0 auto var(--sp-7);
}

.section__head p {
  color: var(--color-ink-soft);
  font-size: var(--fs-md);
  margin: 0;
}

.eyebrow {
  display: inline-block;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  font-size: var(--fs-xs);
  font-weight: 700;
  color: var(--color-accent);
  margin-bottom: var(--sp-2);
}

/* Utility classes */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; }
.mb-0 { margin-bottom: 0; }
.mt-4 { margin-top: var(--sp-4); }
.mt-6 { margin-top: var(--sp-6); }
.muted { color: var(--color-muted); }
.visually-hidden {
  position: absolute !important;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-2);
  font-family: var(--font-sans);
  font-size: var(--fs-sm);
  font-weight: 600;
  line-height: 1;
  padding: 0.8rem 1.4rem;
  border: 2px solid transparent;
  border-radius: var(--radius-pill);
  cursor: pointer;
  transition: all var(--dur) var(--ease);
  text-align: center;
  white-space: nowrap;
}

.btn--primary {
  background: var(--color-accent);
  color: #fff;
}
.btn--primary:hover {
  background: var(--color-accent-dark);
  color: #fff;
}

.btn--secondary {
  background: var(--color-brand);
  color: #fff;
}
.btn--secondary:hover {
  background: var(--color-brand-dark);
  color: #fff;
}

.btn--ghost {
  background: transparent;
  color: var(--color-brand);
  border-color: var(--color-brand);
}
.btn--ghost:hover {
  background: var(--color-brand);
  color: #fff;
}

.btn--light {
  background: #fff;
  color: var(--color-brand);
}
.btn--light:hover {
  background: var(--color-bg-alt);
  color: var(--color-brand-dark);
}

.btn--block {
  display: flex;
  width: 100%;
}

.btn--sm {
  padding: 0.55rem 1rem;
  font-size: var(--fs-xs);
}

/* --------------------------------------------------------------------------
   Header / Nav
   -------------------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--color-line);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-h);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--sp-2);
}

.brand img {
  height: 34px;
  width: auto;
}

.nav {
  display: flex;
  align-items: center;
  gap: var(--sp-5);
}

.nav__list {
  display: flex;
  align-items: center;
  gap: var(--sp-5);
  list-style: none;
  margin: 0;
  padding: 0;
}

.nav__link {
  font-size: var(--fs-sm);
  font-weight: 600;
  color: var(--color-ink);
  padding: var(--sp-2) 0;
  position: relative;
}

.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -2px;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width var(--dur) var(--ease);
}

.nav__link:hover,
.nav__link[aria-current="page"] {
  color: var(--color-brand);
}

.nav__link:hover::after,
.nav__link[aria-current="page"]::after {
  width: 100%;
}

.nav__cta {
  margin-left: var(--sp-3);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 42px;
  height: 42px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--color-line);
  border-radius: var(--radius-sm);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  width: 20px;
  height: 2px;
  margin: 0 auto;
  background: var(--color-ink);
  transition: transform var(--dur) var(--ease), opacity var(--dur) var(--ease);
}

.nav-toggle[aria-expanded="true"] span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}
.nav-toggle[aria-expanded="true"] span:nth-child(2) {
  opacity: 0;
}
.nav-toggle[aria-expanded="true"] span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}

/* --------------------------------------------------------------------------
   Hero
   -------------------------------------------------------------------------- */
.hero {
  background: linear-gradient(135deg, var(--color-brand) 0%, var(--color-brand-dark) 100%);
  color: #fff;
  padding: var(--sp-9) 0;
  position: relative;
  overflow: hidden;
}

.hero::after {
  content: "";
  position: absolute;
  right: -120px;
  top: -80px;
  width: 420px;
  height: 420px;
  background: radial-gradient(circle, rgba(224,114,58,0.35), transparent 70%);
  pointer-events: none;
}

.hero__grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: var(--sp-7);
  align-items: center;
  position: relative;
  z-index: 1;
}

.hero h1 {
  color: #fff;
  font-size: var(--fs-3xl);
  margin-bottom: var(--sp-4);
}

.hero p {
  color: rgba(255, 255, 255, 0.88);
  font-size: var(--fs-md);
  max-width: 42ch;
}

.hero__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
  margin-top: var(--sp-5);
}

.hero__art {
  display: flex;
  justify-content: center;
  gap: var(--sp-4);
}

.hero__art img {
  width: 150px;
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
}

.hero__art img:nth-child(2) {
  margin-top: var(--sp-6);
}

/* --------------------------------------------------------------------------
   Grid / cards
   -------------------------------------------------------------------------- */
.grid {
  display: grid;
  gap: var(--sp-5);
}

.grid--books {
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
}

.grid--authors {
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
}

.grid--genres {
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
}

/* Book card */
.book-card {
  background: var(--color-bg);
  border: 1px solid var(--color-line);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.book-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.book-card__cover {
  aspect-ratio: 2 / 3;
  width: 100%;
  object-fit: cover;
  background: var(--color-bg-alt);
}

.book-card__body {
  padding: var(--sp-4);
  display: flex;
  flex-direction: column;
  flex: 1;
}

.book-card__genre {
  font-size: var(--fs-xs);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-accent);
  font-weight: 700;
  margin-bottom: var(--sp-1);
}

.book-card__title {
  font-family: var(--font-serif);
  font-size: var(--fs-md);
  margin: 0 0 var(--sp-1);
  color: var(--color-ink);
}

.book-card__author {
  font-size: var(--fs-sm);
  color: var(--color-ink-soft);
  margin: 0 0 var(--sp-3);
}

.book-card__foot {
  margin-top: auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.book-card__price {
  font-weight: 700;
  color: var(--color-brand);
}

/* Author card */
.author-card {
  text-align: center;
  background: var(--color-bg);
  border: 1px solid var(--color-line);
  border-radius: var(--radius-lg);
  padding: var(--sp-6) var(--sp-4);
  transition: transform var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.author-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow);
}

.author-card__avatar {
  width: 110px;
  height: 110px;
  border-radius: 50%;
  margin: 0 auto var(--sp-4);
  object-fit: cover;
  border: 3px solid var(--color-bg-alt);
}

.author-card__name {
  font-family: var(--font-serif);
  font-size: var(--fs-md);
  margin: 0 0 var(--sp-1);
}

.author-card__meta {
  font-size: var(--fs-sm);
  color: var(--color-muted);
}

/* Genre tile */
.genre-tile {
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  min-height: 120px;
  padding: var(--sp-4);
  border-radius: var(--radius-lg);
  color: #fff;
  font-family: var(--font-serif);
  font-size: var(--fs-md);
  font-weight: 600;
  background: linear-gradient(135deg, var(--color-brand-light), var(--color-brand-dark));
  transition: transform var(--dur) var(--ease);
}

.genre-tile:hover {
  transform: translateY(-3px);
  color: #fff;
}

.genre-tile:nth-child(2n) {
  background: linear-gradient(135deg, var(--color-accent), var(--color-accent-dark));
}
.genre-tile:nth-child(3n) {
  background: linear-gradient(135deg, #4b6584, #2c3e50);
}

/* --------------------------------------------------------------------------
   Carousel
   -------------------------------------------------------------------------- */
.carousel {
  position: relative;
}

.carousel__viewport {
  overflow: hidden;
}

.carousel__track {
  display: flex;
  gap: var(--sp-5);
  transition: transform 0.4s var(--ease);
  will-change: transform;
}

.carousel__track > * {
  flex: 0 0 auto;
  width: 220px;
}

.carousel__btn {
  position: absolute;
  top: 40%;
  transform: translateY(-50%);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  border: 1px solid var(--color-line);
  background: #fff;
  color: var(--color-brand);
  font-size: 1.3rem;
  cursor: pointer;
  box-shadow: var(--shadow);
  z-index: 2;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background var(--dur) var(--ease);
}

.carousel__btn:hover {
  background: var(--color-bg-alt);
}

.carousel__btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.carousel__btn--prev { left: -18px; }
.carousel__btn--next { right: -18px; }

/* --------------------------------------------------------------------------
   Filter bar (catalog)
   -------------------------------------------------------------------------- */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-3);
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--sp-6);
  padding: var(--sp-4);
  background: var(--color-bg-alt);
  border-radius: var(--radius-lg);
}

.filter-bar__search {
  flex: 1 1 260px;
  min-width: 200px;
}

.chip-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-2);
}

.chip {
  font-size: var(--fs-sm);
  font-weight: 600;
  padding: 0.4rem 0.9rem;
  border-radius: var(--radius-pill);
  border: 1px solid var(--color-line);
  background: #fff;
  color: var(--color-ink-soft);
  cursor: pointer;
  transition: all var(--dur) var(--ease);
}

.chip:hover {
  border-color: var(--color-brand-light);
  color: var(--color-brand);
}

.chip[aria-pressed="true"] {
  background: var(--color-brand);
  border-color: var(--color-brand);
  color: #fff;
}

/* --------------------------------------------------------------------------
   Forms
   -------------------------------------------------------------------------- */
.field {
  margin-bottom: var(--sp-4);
}

.field label {
  display: block;
  font-size: var(--fs-sm);
  font-weight: 600;
  margin-bottom: var(--sp-2);
}

.input,
textarea.input,
select.input {
  width: 100%;
  font-family: var(--font-sans);
  font-size: var(--fs-base);
  padding: 0.75rem 1rem;
  border: 1px solid var(--color-line);
  border-radius: var(--radius);
  background: #fff;
  color: var(--color-ink);
  transition: border-color var(--dur) var(--ease), box-shadow var(--dur) var(--ease);
}

.input:focus,
textarea.input:focus,
select.input:focus {
  outline: none;
  border-color: var(--color-brand-light);
  box-shadow: 0 0 0 3px rgba(58, 114, 166, 0.18);
}

textarea.input {
  min-height: 140px;
  resize: vertical;
}

.form-note {
  margin-top: var(--sp-3);
  padding: var(--sp-3) var(--sp-4);
  border-radius: var(--radius);
  font-size: var(--fs-sm);
  background: var(--color-success-bg);
  color: var(--color-success);
  border: 1px solid rgba(46, 125, 91, 0.3);
}

.form-note[hidden] {
  display: none;
}

/* Newsletter band */
.cta-band {
  background: linear-gradient(135deg, var(--color-brand-dark), var(--color-bg-dark));
  color: #fff;
  border-radius: var(--radius-lg);
  padding: var(--sp-8);
  text-align: center;
}

.cta-band h2 {
  color: #fff;
}

.cta-band p {
  color: rgba(255, 255, 255, 0.85);
  max-width: 46ch;
  margin: 0 auto var(--sp-5);
}

.newsletter-form {
  display: flex;
  gap: var(--sp-3);
  max-width: 460px;
  margin: 0 auto;
  flex-wrap: wrap;
}

.newsletter-form .input {
  flex: 1 1 220px;
}

/* --------------------------------------------------------------------------
   Book / author detail
   -------------------------------------------------------------------------- */
.detail {
  display: grid;
  grid-template-columns: 300px 1fr;
  gap: var(--sp-7);
  align-items: start;
}

.detail__cover {
  width: 100%;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
}

.detail__meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-4);
  margin: var(--sp-4) 0;
  font-size: var(--fs-sm);
  color: var(--color-ink-soft);
}

.detail__meta strong {
  color: var(--color-ink);
}

.detail__price {
  font-size: var(--fs-xl);
  font-weight: 700;
  color: var(--color-brand);
  margin: var(--sp-4) 0;
}

.author-detail {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: var(--sp-6);
  align-items: start;
  margin-bottom: var(--sp-7);
}

.author-detail__avatar {
  width: 180px;
  height: 180px;
  border-radius: 50%;
  object-fit: cover;
  border: 4px solid var(--color-bg-alt);
}

/* Breadcrumb */
.breadcrumb {
  font-size: var(--fs-sm);
  color: var(--color-muted);
  margin-bottom: var(--sp-5);
}

.breadcrumb a { color: var(--color-ink-soft); }

/* Page header band */
.page-head {
  background: var(--color-bg-alt);
  padding: var(--sp-7) 0;
  border-bottom: 1px solid var(--color-line);
  text-align: center;
}

.page-head h1 { margin-bottom: var(--sp-2); }
.page-head p { color: var(--color-ink-soft); margin: 0; }

/* Prose (about, privacy, terms) */
.prose h2 { margin-top: var(--sp-6); }
.prose h3 { margin-top: var(--sp-5); }
.prose p,
.prose li { color: var(--color-ink-soft); }

/* Empty / status state */
.empty-state {
  text-align: center;
  padding: var(--sp-8) var(--sp-4);
  color: var(--color-muted);
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */
.site-footer {
  background: var(--color-bg-dark);
  color: rgba(255, 255, 255, 0.78);
  padding: var(--sp-8) 0 var(--sp-5);
  margin-top: var(--sp-9);
}

.site-footer a {
  color: rgba(255, 255, 255, 0.78);
}
.site-footer a:hover {
  color: #fff;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.6fr repeat(3, 1fr);
  gap: var(--sp-6);
  margin-bottom: var(--sp-6);
}

.footer-brand img {
  height: 32px;
  margin-bottom: var(--sp-3);
  filter: brightness(0) invert(1);
}

.footer-brand p {
  font-size: var(--fs-sm);
  max-width: 34ch;
}

.footer-col h4 {
  color: #fff;
  font-family: var(--font-sans);
  font-size: var(--fs-sm);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: var(--sp-3);
}

.footer-col ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-col li {
  margin-bottom: var(--sp-2);
  font-size: var(--fs-sm);
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.12);
  padding-top: var(--sp-5);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: var(--sp-3);
  font-size: var(--fs-xs);
  color: rgba(255, 255, 255, 0.6);
}

/* --------------------------------------------------------------------------
   Responsive
   -------------------------------------------------------------------------- */
@media (max-width: 900px) {
  .hero__grid { grid-template-columns: 1fr; }
  .hero__art { justify-content: flex-start; margin-top: var(--sp-5); }
  .detail { grid-template-columns: 1fr; }
  .detail__cover { max-width: 260px; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 720px) {
  :root { --fs-3xl: 2.4rem; --fs-2xl: 2rem; }

  .nav-toggle { display: flex; }

  .nav {
    position: fixed;
    top: var(--header-h);
    left: 0;
    right: 0;
    background: #fff;
    border-bottom: 1px solid var(--color-line);
    box-shadow: var(--shadow);
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: var(--sp-3) var(--sp-5) var(--sp-5);
    transform: translateY(-8px);
    opacity: 0;
    visibility: hidden;
    transition: opacity var(--dur) var(--ease), transform var(--dur) var(--ease), visibility var(--dur);
  }

  .nav.is-open {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
  }

  .nav__list {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    width: 100%;
  }

  .nav__link {
    display: block;
    padding: var(--sp-3) 0;
    border-bottom: 1px solid var(--color-line);
  }

  .nav__link::after { display: none; }

  .nav__cta {
    margin: var(--sp-4) 0 0;
    width: 100%;
  }

  .author-detail {
    grid-template-columns: 1fr;
    justify-items: center;
    text-align: center;
  }

  .footer-grid { grid-template-columns: 1fr; }
}

@media (max-width: 460px) {
  .grid--books { grid-template-columns: 1fr 1fr; }
  .hero__art img { width: 120px; }
  .newsletter-form { flex-direction: column; }
}