/* ==========================================================================
   SK CORE — landing page stylesheet
   Dark theme by default, light theme via [data-theme="light"].
   No external fonts or assets are requested: system font stack + inline SVG.
   ========================================================================== */

:root {
  color-scheme: dark;

  --bg: #0b1220;
  --bg-soft: #0e1729;
  --panel: #101b2e;
  --panel-hover: #14223a;
  --line: #1d2c45;
  --line-strong: #2b3f60;
  --text: #e9effa;
  --muted: #a6b6ce;
  --dim: #7f90a9;
  --brand: #5b8cff;
  --brand-strong: #85aaff;
  --brand-contrast: #061024;
  --ok: #4ade80;
  --ok-soft: rgba(74, 222, 128, 0.12);
  --warn: #fbbf24;
  --warn-soft: rgba(251, 191, 36, 0.12);
  --shadow: 0 20px 45px rgba(3, 8, 20, 0.55);
  --shadow-sm: 0 6px 18px rgba(3, 8, 20, 0.35);

  --container: 1120px;
  --radius: 16px;
  --radius-sm: 10px;
  --radius-pill: 999px;

  --font-sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

[data-theme="light"] {
  color-scheme: light;

  --bg: #f6f8fb;
  --bg-soft: #eef2f8;
  --panel: #ffffff;
  --panel-hover: #f8fafd;
  --line: #dde5f0;
  --line-strong: #c3d0e2;
  --text: #101c30;
  --muted: #4c5c75;
  --dim: #5b6a81;
  --brand: #1f4fd8;
  --brand-strong: #163f9f;
  --brand-contrast: #ffffff;
  --ok: #127037;
  --ok-soft: rgba(21, 128, 61, 0.10);
  --warn: #8a5406;
  --warn-soft: rgba(161, 98, 7, 0.10);
  --shadow: 0 18px 40px rgba(16, 28, 48, 0.10);
  --shadow-sm: 0 4px 14px rgba(16, 28, 48, 0.08);
}

/* --------------------------------------------------------------- baseline */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 5.5rem;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3 {
  margin: 0 0 0.5em;
  line-height: 1.2;
  letter-spacing: -0.015em;
  font-weight: 650;
}

h1 { font-size: clamp(2rem, 4.4vw, 3.15rem); }
h2 { font-size: clamp(1.4rem, 2.6vw, 1.95rem); }
h3 { font-size: 1.12rem; }

p { margin: 0 0 1rem; }

a { color: var(--brand-strong); text-decoration: none; }
a:hover { text-decoration: underline; }

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

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

:focus-visible {
  outline: 2px solid var(--brand-strong);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ----------------------------------------------------------------- layout */

.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 1.25rem;
}

.section { padding: 4.5rem 0; }
.section--tight { padding: 3rem 0; }

.section-head { max-width: 62ch; margin-bottom: 2.25rem; }
.section-head p { color: var(--muted); margin-bottom: 0; }

.eyebrow {
  display: inline-block;
  margin: 0 0 0.75rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--brand-strong);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  padding: 0.7rem 1rem;
  border-radius: 0 0 var(--radius-sm) 0;
  background: var(--brand);
  color: var(--brand-contrast);
  font-weight: 600;
}
.skip-link:focus { left: 0; }

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

/* ----------------------------------------------------------------- header */

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  border-bottom: 1px solid var(--line);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: saturate(140%) blur(10px);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: 1rem;
  min-height: 4rem;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.65rem;
  color: var(--text);
  font-weight: 650;
  letter-spacing: 0.02em;
}
.brand:hover { text-decoration: none; }
.brand__mark { color: var(--brand); flex: none; }
.brand__name { font-size: 1.02rem; }
.brand__name b { font-weight: 700; }
.brand__sub {
  display: block;
  font-size: 0.68rem;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--dim);
}

.site-nav { margin-left: auto; display: flex; align-items: center; gap: 0.35rem; }

.nav-list { display: flex; align-items: center; gap: 0.25rem; }

.nav-link {
  display: inline-block;
  padding: 0.5rem 0.7rem;
  border-radius: var(--radius-sm);
  color: var(--muted);
  font-size: 0.95rem;
  font-weight: 500;
}
.nav-link:hover { color: var(--text); background: var(--panel-hover); text-decoration: none; }
.nav-link[aria-current="page"] { color: var(--text); }

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.35rem;
  height: 2.35rem;
  margin-left: 0.35rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel);
  color: var(--muted);
  cursor: pointer;
}
.theme-toggle:hover { color: var(--text); border-color: var(--line-strong); }
.theme-toggle svg { width: 18px; height: 18px; }
.theme-toggle .icon-sun { display: none; }
[data-theme="light"] .theme-toggle .icon-sun { display: block; }
[data-theme="light"] .theme-toggle .icon-moon { display: none; }

.nav-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.35rem;
  height: 2.35rem;
  margin-left: auto;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
}
.nav-toggle svg { width: 20px; height: 20px; }

/* -------------------------------------------------------------- hero/about */

.hero {
  position: relative;
  padding: 5rem 0 4rem;
  border-bottom: 1px solid var(--line);
  background:
    radial-gradient(1100px 420px at 18% -10%, color-mix(in srgb, var(--brand) 14%, transparent), transparent 70%),
    var(--bg);
}

.hero__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: 3rem;
  align-items: center;
}

.hero p.hero__sub {
  max-width: 52ch;
  color: var(--muted);
  font-size: 1.06rem;
  margin-bottom: 1.75rem;
}

.hero__actions { display: flex; flex-wrap: wrap; gap: 0.75rem; }

.hero__hint {
  margin-top: 1.5rem;
  font-size: 0.86rem;
  color: var(--dim);
}

/* Ecosystem diagram: products -> SK CORE -> destination websites */
.orbit {
  position: relative;
  padding: 1.5rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  box-shadow: var(--shadow-sm);
}

.orbit__title {
  margin: 0 0 1rem;
  font-size: 0.76rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--dim);
}

.orbit__rows { display: grid; gap: 0.6rem; }

.orbit__row {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 0.6rem;
  padding: 0.7rem 0.8rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--bg-soft);
  font-size: 0.9rem;
}

.orbit__node { color: var(--text); font-weight: 550; }
.orbit__node--muted { color: var(--dim); font-weight: 500; }
.orbit__arrow { color: var(--brand); font-family: var(--font-mono); }
.orbit__center {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 0.9rem;
  padding-top: 0.9rem;
  border-top: 1px dashed var(--line-strong);
  color: var(--muted);
  font-size: 0.82rem;
}
.orbit__center svg { width: 22px; height: 22px; color: var(--brand); }

.about__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 2.5rem;
  align-items: start;
}

.about__points li {
  position: relative;
  padding-left: 1.6rem;
  margin-bottom: 0.7rem;
  color: var(--muted);
}
.about__points li::before {
  content: "";
  position: absolute;
  left: 0.15rem;
  top: 0.55rem;
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 50%;
  background: var(--brand);
}

/* --------------------------------------------------------------- products */

.product-group + .product-group { margin-top: 2.75rem; }

.product-group__heading {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  margin-bottom: 1.1rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--dim);
}
.product-group__heading::after {
  content: "";
  flex: 1;
  height: 1px;
  background: var(--line);
}

.product-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1.25rem;
}

.product-card {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 0.9rem;
  padding: 1.4rem;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--panel);
  transition: transform 140ms ease, border-color 140ms ease, box-shadow 140ms ease, background-color 140ms ease;
}
.product-card:hover {
  transform: translateY(-2px);
  border-color: var(--line-strong);
  box-shadow: var(--shadow);
}
.product-card:focus-within { border-color: var(--brand); box-shadow: var(--shadow); }
.product-card--unavailable { background: var(--bg-soft); }
.product-card--unavailable:hover { transform: none; box-shadow: var(--shadow-sm); border-color: var(--line); }

.product-card__head { display: flex; align-items: flex-start; gap: 0.9rem; }

.product-card__icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: none;
  width: 2.9rem;
  height: 2.9rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--bg-soft);
  color: var(--brand);
}
.product-card__icon svg { width: 26px; height: 26px; }

.product-card__titles { min-width: 0; flex: 1; }

.product-card__name { margin: 0; font-size: 1.06rem; letter-spacing: -0.01em; }

.product-card__cat {
  margin: 0.15rem 0 0;
  font-size: 0.8rem;
  color: var(--dim);
}

.product-card__badge { flex: none; margin-left: auto; }

.product-card__tagline { margin: 0; font-weight: 550; }

.product-card__desc { margin: 0; color: var(--muted); font-size: 0.93rem; }

.chips { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.chip {
  padding: 0.25rem 0.6rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-pill);
  background: var(--bg-soft);
  color: var(--muted);
  font-size: 0.78rem;
}

.product-card__foot {
  margin-top: auto;
  padding-top: 0.9rem;
  border-top: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.product-card__note {
  margin: 0;
  font-size: 0.82rem;
  color: var(--dim);
}

/* --------------------------------------------------------------- controls */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.7rem 1.15rem;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  font: inherit;
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  text-align: center;
}
.btn:hover { text-decoration: none; }
.btn svg { width: 16px; height: 16px; }

.btn--primary { background: var(--brand); color: var(--brand-contrast); }
.btn--primary:hover { background: var(--brand-strong); }

.btn--ghost { background: transparent; border-color: var(--line-strong); color: var(--text); }
.btn--ghost:hover { background: var(--panel-hover); }

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

.btn--disabled,
.btn[aria-disabled="true"] {
  background: var(--bg-soft);
  border-color: var(--line);
  color: var(--dim);
  cursor: not-allowed;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  padding: 0.2rem 0.55rem;
  border: 1px solid var(--line);
  border-radius: var(--radius-pill);
  font-size: 0.74rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  white-space: nowrap;
}
.badge::before {
  content: "";
  width: 0.45rem;
  height: 0.45rem;
  border-radius: 50%;
  background: currentColor;
}
.badge--available { color: var(--ok); background: var(--ok-soft); border-color: color-mix(in srgb, var(--ok) 35%, transparent); }
.badge--pending { color: var(--warn); background: var(--warn-soft); border-color: color-mix(in srgb, var(--warn) 35%, transparent); }

/* Stretched card link: the whole card is clickable, one link in the tab order. */
.card-link::after {
  content: "";
  position: absolute;
  inset: 0;
  border-radius: var(--radius);
}

/* ----------------------------------------------------------------- footer */

.site-footer {
  border-top: 1px solid var(--line);
  background: var(--bg-soft);
  padding: 2.75rem 0 2rem;
  font-size: 0.9rem;
}

.site-footer__grid {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) repeat(auto-fit, minmax(150px, 1fr));
  gap: 2rem;
}

.site-footer__brand { display: flex; align-items: center; gap: 0.6rem; margin-bottom: 0.75rem; }
.site-footer__brand .brand__mark { color: var(--brand); }
.site-footer__note { color: var(--dim); max-width: 42ch; margin: 0; }

.site-footer h2 {
  margin: 0 0 0.75rem;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--dim);
}

.site-footer li { margin-bottom: 0.45rem; }
.site-footer a { color: var(--muted); }
.site-footer a:hover { color: var(--text); }

.site-footer__bottom {
  margin-top: 2.25rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1.5rem;
  align-items: center;
  justify-content: space-between;
  color: var(--dim);
  font-size: 0.84rem;
}
.site-footer__bottom p { margin: 0; }

/* -------------------------------------------------------------------- 404 */

.error-page {
  display: flex;
  align-items: center;
  min-height: calc(100vh - 4rem);
  padding: 4rem 0;
}
.error-page__inner { max-width: 54ch; }
.error-page__code {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--brand-strong);
}
.error-page__actions { display: flex; flex-wrap: wrap; gap: 0.75rem; margin-top: 1.75rem; }

/* ------------------------------------------------------------- responsive */

@media (max-width: 900px) {
  .hero__grid { grid-template-columns: 1fr; gap: 2.25rem; }
  .about__grid { grid-template-columns: 1fr; gap: 1.75rem; }
}

@media (max-width: 720px) {
  .js .nav-toggle { display: inline-flex; }

  .site-nav {
    position: absolute;
    left: 0;
    right: 0;
    top: 100%;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0.35rem;
    padding: 0.9rem 1.25rem 1.1rem;
    border-bottom: 1px solid var(--line);
    background: var(--bg);
    box-shadow: var(--shadow-sm);
  }
  .site-nav[data-open="true"] { display: flex; }

  .nav-list { flex-direction: column; align-items: stretch; gap: 0.3rem; }
  .nav-link { padding: 0.7rem 0.75rem; font-size: 1rem; }

  .theme-toggle { margin-left: 0; align-self: flex-start; }

  .section { padding: 3.25rem 0; }
  .hero { padding: 3.25rem 0 3rem; }
  .product-grid { grid-template-columns: 1fr; }
  .site-footer__grid { grid-template-columns: 1fr; gap: 1.5rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
  .product-card:hover { transform: none; }
}

@media (prefers-contrast: more) {
  :root { --line: #3a4f74; --muted: #d3dded; }
  [data-theme="light"] { --line: #8fa3c0; --muted: #2c3b52; }
}

/* Entrance animation: CSS only, no JavaScript. */
@media (prefers-reduced-motion: no-preference) {
  .hero__copy > *, .orbit { animation: sk-rise 420ms ease both; }
  .orbit { animation-delay: 90ms; }
}

@keyframes sk-rise {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: none; }
}