/* ForgeSpec landing page — forgespec.io */

:root {
  --color-bg: #0a0a0b;
  --color-bg-elevated: #111114;
  --color-text: #f0f0f2;
  --color-text-muted: #a8a8b0;
  --color-text-dim: #5c5c66;
  --color-accent: #8b93c9;
  --color-accent-dim: #6e759f;
  --color-border: #2a2a32;
  --color-border-light: #3d3d48;

  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;

  --space-xs: 0.5rem;
  --space-sm: 1rem;
  --space-md: 1.5rem;
  --space-lg: 2.5rem;
  --space-xl: 4rem;

  --header-height: 4.5rem;
  --max-width: 72rem;
  --radius: 4px;
}

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.6;
  color: var(--color-text-muted);
  background-color: var(--color-bg);
  background-image:
    linear-gradient(rgba(139, 147, 201, 0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(139, 147, 201, 0.03) 1px, transparent 1px),
    radial-gradient(ellipse 80% 50% at 70% 40%, rgba(139, 147, 201, 0.06), transparent 60%),
    radial-gradient(ellipse 60% 40% at 20% 80%, rgba(139, 147, 201, 0.04), transparent 50%);
  background-size: 48px 48px, 48px 48px, 100% 100%, 100% 100%;
  background-position: center top;
  -webkit-font-smoothing: antialiased;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: 0.35;
  background-image: url("assets/bg-circuit.svg");
  background-size: cover;
  background-position: center;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-sm);
  z-index: 1000;
  padding: 0.5rem 1rem;
  background: var(--color-accent);
  color: var(--color-bg);
  text-decoration: none;
  border-radius: var(--radius);
}

.skip-link:focus {
  top: var(--space-sm);
}

/* Header */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  height: var(--header-height);
  background: rgba(10, 10, 11, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(42, 42, 50, 0.6);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: var(--max-width);
  height: 100%;
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.logo {
  font-size: 1.125rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-decoration: none;
  color: var(--color-text);
}

.logo-forge,
.title-forge {
  color: var(--color-text);
}

.logo-spec,
.title-spec {
  color: var(--color-accent);
}

.site-nav ul {
  display: flex;
  gap: var(--space-lg);
  margin: 0;
  padding: 0;
  list-style: none;
}

.site-nav a {
  font-size: 0.8125rem;
  font-weight: 500;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--color-text);
  transition: color 0.2s ease;
}

.site-nav a:hover,
.site-nav a:focus-visible {
  color: var(--color-accent);
}

/* Anchor scroll offset (fixed header) */

#hero,
#book,
#about {
  scroll-margin-top: var(--header-height);
}

/* Hero */

.hero {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  padding-top: var(--header-height);
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
  align-items: center;
  flex: 1;
  max-width: var(--max-width);
  width: 100%;
  margin: 0 auto;
  padding: var(--space-lg) var(--space-lg) var(--space-xl);
}

.hero-content {
  max-width: 34rem;
}

.hero-title {
  margin: 0 0 var(--space-sm);
  font-size: clamp(2.75rem, 6vw, 4.5rem);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: 0.06em;
}

.hero-subtitle {
  margin: 0;
  font-size: clamp(1rem, 2.2vw, 1.25rem);
  font-weight: 600;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--color-text);
}

.hero-divider {
  width: 3rem;
  height: 2px;
  margin: var(--space-md) 0;
  border: none;
  background: var(--color-accent);
}

.hero-tagline {
  margin: 0 0 var(--space-md);
  font-size: clamp(1.05rem, 2vw, 1.2rem);
  font-weight: 500;
  color: var(--color-accent);
}

.hero-description {
  margin: 0 0 var(--space-md);
  font-size: 1.05rem;
  line-height: 1.65;
  color: var(--color-text-muted);
}

.hero-list {
  margin: 0 0 var(--space-lg);
  padding: 0;
  list-style: none;
}

.hero-list li {
  position: relative;
  padding-left: 1.75rem;
  margin-bottom: var(--space-xs);
  color: var(--color-text-muted);
}

.hero-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 0.55em;
  width: 0.55rem;
  height: 0.3rem;
  border-left: 2px solid var(--color-accent);
  border-bottom: 2px solid var(--color-accent);
  transform: rotate(-45deg) translateY(-1px);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.35rem;
  font-family: inherit;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  text-decoration: none;
  border-radius: var(--radius);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background-color 0.2s ease, border-color 0.2s ease, color 0.2s ease;
}

.btn-primary {
  background: var(--color-accent);
  color: var(--color-bg);
  border-color: var(--color-accent);
}

.btn-primary:hover,
.btn-primary:focus-visible {
  background: #9ba3d4;
  border-color: #9ba3d4;
  color: var(--color-bg);
}

.btn-secondary {
  background: transparent;
  color: var(--color-text);
  border-color: var(--color-border-light);
}

.btn-secondary:hover,
.btn-secondary:focus-visible {
  border-color: var(--color-accent);
  color: var(--color-accent);
}

.btn-icon {
  flex-shrink: 0;
}

/* Hero book image — pre-rendered 3D (desktop) / flat cover (narrow) via <picture> */

.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
  max-width: 100%;
  min-width: 0;
}

.book-figure {
  margin: 0;
  padding: var(--space-md);
  max-width: 100%;
}

.book-picture {
  display: block;
  max-width: 100%;
  line-height: 0;
}

.book-cover {
  display: block;
  width: auto;
  height: auto;
  max-width: 100%;
  transform: none;
  filter: drop-shadow(0 24px 70px rgba(0, 0, 0, 0.55));
}

@media (min-width: 900px) {
  .book-cover {
    width: min(26rem, 48vw);
  }
}

@media (max-width: 899px) {
  .book-cover {
    width: min(16rem, 42vw);
    filter: drop-shadow(0 20px 56px rgba(0, 0, 0, 0.5));
  }
}

/* Scroll hint */

.scroll-hint {
  display: flex;
  justify-content: center;
  padding-bottom: var(--space-md);
  color: var(--color-accent-dim);
  text-decoration: none;
  opacity: 0.7;
  transition: opacity 0.2s ease, color 0.2s ease;
}

.scroll-hint:hover,
.scroll-hint:focus-visible {
  opacity: 1;
  color: var(--color-accent);
}

/* Book availability */

.book-section {
  position: relative;
  z-index: 1;
  padding: var(--space-lg) var(--space-lg);
  border-top: 1px solid var(--color-border);
  text-align: center;
}

.book-section-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.book-section h2 {
  margin: 0 0 var(--space-sm);
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--color-text-dim);
}

.book-availability {
  margin: 0;
  font-size: clamp(1.125rem, 2.5vw, 1.375rem);
  font-weight: 500;
  color: var(--color-accent);
  letter-spacing: 0.02em;
}

.book-order {
  margin: var(--space-md) 0 0;
}

/* About */

.about {
  position: relative;
  z-index: 1;
  padding: var(--space-xl) var(--space-lg);
  border-top: 1px solid var(--color-border);
  background: rgba(17, 17, 20, 0.6);
}

.about-inner {
  max-width: 40rem;
  margin: 0 auto;
}

.about h2 {
  margin: 0 0 var(--space-md);
  font-size: clamp(1.5rem, 3vw, 1.875rem);
  font-weight: 600;
  letter-spacing: 0.04em;
  color: var(--color-text);
}

.about p {
  margin: 0 0 var(--space-md);
  font-size: 1.05rem;
  line-height: 1.7;
}

.about-audience {
  margin: var(--space-md) 0 var(--space-lg);
  padding: 0;
  list-style: none;
}

.about-audience li {
  position: relative;
  padding-left: 1.25rem;
  margin-bottom: var(--space-xs);
}

.about-audience li::before {
  content: "—";
  position: absolute;
  left: 0;
  color: var(--color-accent-dim);
}

.about-order a,
.about-github a {
  font-size: 0.9375rem;
  color: var(--color-accent-dim);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 0.2s ease, border-color 0.2s ease;
}

.about-order a:hover,
.about-order a:focus-visible,
.about-github a:hover,
.about-github a:focus-visible {
  color: var(--color-accent);
  border-bottom-color: var(--color-accent);
}

/* Footer */

.site-footer {
  position: relative;
  z-index: 1;
  padding: var(--space-lg);
  text-align: center;
  border-top: 1px solid var(--color-border);
}

.site-footer p {
  margin: 0;
  font-size: 0.8125rem;
  color: var(--color-text-dim);
}

/* Focus */

a:focus-visible,
.btn:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 3px;
}

/* Tablet */

@media (max-width: 900px) {
  .hero-inner {
    grid-template-columns: 1fr;
    gap: var(--space-lg);
    text-align: center;
    padding-top: var(--space-md);
  }

  .hero-content {
    max-width: none;
    margin: 0 auto;
  }

  .hero-divider {
    margin-left: auto;
    margin-right: auto;
  }

  .hero-actions {
    justify-content: center;
  }

  .hero-list li {
    text-align: left;
    max-width: 20rem;
    margin-left: auto;
    margin-right: auto;
  }

}


/* Mobile */

@media (max-width: 600px) {
  :root {
    --header-height: 3.75rem;
  }

  .header-inner {
    padding: 0 var(--space-sm);
  }

  .site-nav ul {
    gap: var(--space-sm);
  }

  .site-nav a {
    font-size: 0.7rem;
    letter-spacing: 0.1em;
  }

  .logo {
    font-size: 0.95rem;
  }

  .hero-inner {
    padding: var(--space-sm) var(--space-sm) var(--space-lg);
  }

  .hero-title {
    letter-spacing: 0.04em;
  }

  .hero-subtitle {
    letter-spacing: 0.14em;
  }

  .hero-actions {
    flex-direction: column;
    align-items: stretch;
  }

  .btn {
    width: 100%;
  }

  .book-cover {
    width: min(14rem, 70vw);
    filter: drop-shadow(0 16px 48px rgba(0, 0, 0, 0.5));
  }

  .about {
    padding: var(--space-lg) var(--space-sm);
  }
}