:root,
[data-theme='light'] {
  --text-xs: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);
  --text-sm: clamp(0.875rem, 0.8rem + 0.35vw, 1rem);
  --text-base: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  --text-lg: clamp(1.125rem, 1rem + 0.75vw, 1.5rem);
  --text-xl: clamp(1.5rem, 1.2rem + 1.25vw, 2.25rem);
  --text-2xl: clamp(2rem, 1.2rem + 2.5vw, 3.5rem);
  --text-3xl: clamp(2.5rem, 1rem + 4vw, 5rem);

  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;
  --space-20: 5rem;
  --space-24: 6rem;
  --space-32: 8rem;

  --font-display: 'Boska', Georgia, serif;
  --font-body: 'Satoshi', system-ui, sans-serif;

  --color-bg: #dceef8;
  --color-surface: #f7fbfd;
  --color-surface-2: #ecf7fc;
  --color-surface-offset: #c9e4f2;
  --color-border: #a8cadc;
  --color-text: #1c2a32;
  --color-text-muted: #536775;
  --color-text-faint: #7692a1;
  --color-text-inverse: #ffffff;
  --color-primary: #1f6079;
  --color-primary-hover: #164b60;
  --color-primary-active: #103747;
  --color-primary-highlight: #d7ebf5;
  --color-warning: #8a4a21;
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;
  --shadow-sm: 0 1px 2px oklch(0.25 0.02 220 / 0.08);
  --shadow-md: 0 8px 24px oklch(0.25 0.02 220 / 0.12);
  --shadow-lg: 0 24px 60px oklch(0.25 0.02 220 / 0.18);
  --transition-interactive: 180ms cubic-bezier(0.16, 1, 0.3, 1);
  --content-narrow: 640px;
  --content-default: 960px;
  --content-wide: 1180px;
}

[data-theme='dark'] {
  --color-bg: #101a20;
  --color-surface: #16252d;
  --color-surface-2: #1b2d37;
  --color-surface-offset: #213642;
  --color-border: #355262;
  --color-text: #e7f2f7;
  --color-text-muted: #adc2ce;
  --color-text-faint: #7893a1;
  --color-text-inverse: #101a20;
  --color-primary: #8ccce7;
  --color-primary-hover: #a7dcf1;
  --color-primary-active: #c1e8f6;
  --color-primary-highlight: #213642;
  --color-warning: #e3a56f;
  --shadow-sm: 0 1px 2px oklch(0 0 0 / 0.24);
  --shadow-md: 0 8px 24px oklch(0 0 0 / 0.3);
  --shadow-lg: 0 24px 60px oklch(0 0 0 / 0.42);
}

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

html {
  -moz-text-size-adjust: none;
  -webkit-text-size-adjust: none;
  text-size-adjust: none;
  scroll-behavior: smooth;
  scroll-padding-top: var(--space-16);
}

body {
  min-height: 100dvh;
  line-height: 1.6;
  font-family: var(--font-body);
  font-size: var(--text-base);
  color: var(--color-text);
  background:
    radial-gradient(circle at 50% 0%, color-mix(in oklab, var(--color-surface) 76%, transparent), transparent 32rem),
    var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a,
button,
input {
  transition:
    color var(--transition-interactive),
    background var(--transition-interactive),
    border-color var(--transition-interactive),
    box-shadow var(--transition-interactive),
    transform var(--transition-interactive);
}

button,
input {
  font: inherit;
}

button {
  cursor: pointer;
  border: 0;
}

:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

.skip-link {
  position: absolute;
  left: var(--space-4);
  top: var(--space-4);
  z-index: 100;
  transform: translateY(-150%);
  border-radius: var(--radius-full);
  background: var(--color-primary);
  color: var(--color-text-inverse);
  padding: var(--space-2) var(--space-4);
}

.skip-link:focus {
  transform: translateY(0);
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: var(--space-4);
  background: color-mix(in oklab, var(--color-bg) 86%, transparent);
  backdrop-filter: blur(16px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--color-text);
  text-decoration: none;
  font-size: var(--text-sm);
  font-weight: 700;
  letter-spacing: 0.02em;
}

.brand-mark {
  width: 2.25rem;
  color: var(--color-primary);
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.header-actions a {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  font-weight: 700;
  text-decoration: none;
}

.header-actions a:hover {
  color: var(--color-primary);
}

.theme-toggle {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border: 1px solid color-mix(in oklab, var(--color-text) 14%, transparent);
  border-radius: var(--radius-full);
  background: color-mix(in oklab, var(--color-surface) 84%, transparent);
  color: var(--color-text);
}

.theme-toggle:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: var(--space-12);
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: clamp(var(--space-8), 7vw, var(--space-20)) var(--space-4) var(--space-16);
}

.hero-copy {
  display: grid;
  gap: var(--space-6);
  max-width: 740px;
}

.eyebrow {
  color: var(--color-primary);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.16em;
  line-height: 1.3;
  text-transform: uppercase;
}

h1,
h2 {
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.02;
  letter-spacing: -0.03em;
}

h1 {
  font-size: var(--text-2xl);
  max-width: 12ch;
}

h2 {
  font-size: var(--text-xl);
}

h3 {
  font-size: var(--text-lg);
  line-height: 1.2;
}

p {
  max-width: 72ch;
}

.hero-lede {
  color: var(--color-text-muted);
  font-size: var(--text-base);
  max-width: 64ch;
}

.signup-card {
  display: grid;
  gap: var(--space-4);
  width: min(100%, 680px);
  border: 1px solid color-mix(in oklab, var(--color-text) 12%, transparent);
  border-radius: var(--radius-xl);
  background: color-mix(in oklab, var(--color-surface) 94%, transparent);
  box-shadow: var(--shadow-md);
  padding: clamp(var(--space-5), 4vw, var(--space-8));
}

.signup-card h2 {
  font-family: var(--font-body);
  font-size: var(--text-lg);
  letter-spacing: -0.02em;
}

.signup-card p,
.form-note {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
}

.signup-card label {
  color: var(--color-text);
  font-size: var(--text-sm);
  font-weight: 700;
}

.form-row {
  display: grid;
  gap: var(--space-3);
}

.form-row input {
  min-height: 52px;
  width: 100%;
  border: 1px solid color-mix(in oklab, var(--color-text) 16%, transparent);
  border-radius: var(--radius-md);
  background: var(--color-surface);
  color: var(--color-text);
  padding: var(--space-3) var(--space-4);
}

.form-row input::placeholder {
  color: var(--color-text-faint);
}

.form-row button,
.primary-link {
  min-height: 52px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  background: var(--color-primary);
  color: var(--color-text-inverse);
  font-size: var(--text-sm);
  font-weight: 700;
  padding: var(--space-3) var(--space-5);
}

.form-row button:hover,
.primary-link:hover {
  background: var(--color-primary-hover);
}

.cover-stack {
  display: grid;
  justify-items: center;
}

.cover-card {
  width: min(100%, 340px);
  border-radius: var(--radius-xl);
  background: var(--color-surface);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
}

.cover-card img {
  width: 100%;
}

.cover-card figcaption {
  padding: var(--space-3) var(--space-4);
  color: var(--color-text-muted);
  font-size: var(--text-xs);
  font-weight: 700;
  line-height: 1.35;
}

.reader-promise,
.book-links,
.about-author {
  max-width: var(--content-wide);
  margin-inline: auto;
  padding: clamp(var(--space-10), 6vw, var(--space-20)) var(--space-4);
}

.section-heading {
  display: grid;
  gap: var(--space-3);
  margin-bottom: var(--space-8);
}

.section-heading p {
  color: var(--color-text-muted);
}

.centered {
  justify-items: center;
  text-align: center;
  margin-inline: auto;
}

.promise-grid {
  display: grid;
  gap: var(--space-4);
}

.promise-grid article {
  display: grid;
  gap: var(--space-3);
  border-radius: var(--radius-lg);
  background: color-mix(in oklab, var(--color-surface) 78%, transparent);
  box-shadow: var(--shadow-sm);
  padding: var(--space-6);
}

.promise-grid p,
.about-author p {
  color: var(--color-text-muted);
}

.about-author {
  display: grid;
  gap: var(--space-6);
  border-block: 1px solid color-mix(in oklab, var(--color-text) 12%, transparent);
}

.books-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: var(--space-4);
}

.book-card {
  display: grid;
  gap: var(--space-3);
  align-content: start;
  color: var(--color-text);
  text-align: center;
  text-decoration: none;
}

.book-card img {
  width: 100%;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
}

.book-card span {
  font-size: var(--text-sm);
  font-weight: 700;
  line-height: 1.3;
}

.book-card:hover {
  color: var(--color-primary);
}

.book-card:hover img {
  transform: translateY(-2px);
}

.site-footer {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-3) var(--space-6);
  padding: var(--space-8) var(--space-4);
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  text-align: center;
}

.site-footer a {
  color: var(--color-primary);
  font-weight: 700;
}

@media (min-width: 680px) {
  .form-row {
    grid-template-columns: 1fr auto;
  }

  .books-grid {
    grid-template-columns: repeat(4, minmax(0, 1fr));
  }
}

@media (min-width: 920px) {
  .hero {
    grid-template-columns: minmax(0, 1.08fr) minmax(320px, 0.72fr);
    align-items: center;
  }

  .cover-stack {
    justify-items: end;
  }

  .cover-card {
    width: min(100%, 340px);
  }

  .promise-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .wide-card {
    grid-column: span 1;
  }

  .about-author {
    grid-template-columns: 0.88fr 1fr;
    align-items: start;
  }
}

@media (max-width: 520px) {
  .header-actions a {
    display: none;
  }

  .hero {
    padding-top: var(--space-8);
  }

  h1 {
    max-width: 100%;
  }

  .cover-card {
    width: min(100%, 300px);
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
  }
}