/* =========================================================================
   Sessyn design system — "Instrument"
   =========================================================================
   Direction: a precision measuring instrument, not a security scare ad.
   Near-black chassis, luminous readouts, data rendered as the decoration.

   Manifesto constraints encoded here:
     §5  dark-first with real light mode, sparing luminous accents,
         WCAG-conscious contrast, reduced-motion support
     §5  no third-party fonts, trackers, or marketing tags — every byte is
         first-party, which is why the type stack is local-only
     §51 keyboard navigation, visible focus, no meaning by colour alone
   ========================================================================= */

/* ---------- Tokens ---------- */

:root {
  /* Chassis — near-black, cool-shifted, never pure #000 */
  --s-void: #06070a;
  --s-base: #0a0c11;
  --s-surface: #10131a;
  --s-raised: #171b24;
  --s-line: #232834;
  --s-line-bright: #323949;

  /* Readouts — luminous, used sparingly and never as the only signal */
  --s-signal: #4fd6e8; /* cyan: allowed / measured */
  --s-signal-dim: #2a8d9b;
  --s-warn: #f2a65a; /* amber: restricted / caution */
  --s-stop: #ff6b6b; /* coral: blocked */
  --s-ok: #7ee08a; /* green: essential, kept working */

  /* Ink */
  --s-ink: #eef1f7;
  --s-ink-mid: #a8b0c0;
  --s-ink-dim: #6d7688;

  /* Type — local stacks only. Mono-forward: this is an instrument. */
  --s-display: ui-sans-serif, "Helvetica Neue", "Arial Narrow", system-ui, sans-serif;
  --s-mono: ui-monospace, "SF Mono", "Cascadia Mono", "Roboto Mono", Menlo, Consolas, monospace;

  /* Scale — fluid, generous */
  --s-step--1: clamp(0.78rem, 0.76rem + 0.1vw, 0.84rem);
  --s-step-0: clamp(0.95rem, 0.92rem + 0.16vw, 1.05rem);
  --s-step-1: clamp(1.2rem, 1.1rem + 0.5vw, 1.5rem);
  --s-step-2: clamp(1.6rem, 1.35rem + 1.2vw, 2.4rem);
  --s-step-3: clamp(2.2rem, 1.6rem + 2.8vw, 4rem);
  --s-step-4: clamp(2.8rem, 1.7rem + 5.2vw, 6.5rem);

  /* Space */
  --s-1: 0.25rem;
  --s-2: 0.5rem;
  --s-3: 0.75rem;
  --s-4: 1rem;
  --s-6: 1.5rem;
  --s-8: 2rem;
  --s-12: 3rem;
  --s-16: 4rem;
  --s-24: 6rem;
  --s-32: 8rem;

  --s-radius: 3px;
  --s-radius-lg: 6px;
  --s-rule: 1px solid var(--s-line);

  --s-measure: 68ch;
  --s-page: 1240px;

  --s-ease: cubic-bezier(0.22, 0.61, 0.36, 1);
  --s-dur: 280ms;
}

/* Light mode is a genuine mode, not an afterthought (§5). */
@media (prefers-color-scheme: light) {
  :root:not([data-theme='dark']) {
    --s-void: #eef0f4;
    --s-base: #f7f8fa;
    --s-surface: #ffffff;
    --s-raised: #ffffff;
    --s-line: #d9dde6;
    --s-line-bright: #b9c0cd;
    --s-signal: #0d7f8f;
    --s-signal-dim: #0d7f8f;
    --s-warn: #a35d12;
    --s-stop: #c0392b;
    --s-ok: #1f7a34;
    --s-ink: #0e1116;
    --s-ink-mid: #444d5c;
    --s-ink-dim: #6b7383;
  }
}

/* ---------- Reset ---------- */

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

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

body {
  margin: 0;
  background: var(--s-base);
  color: var(--s-ink);
  font-family: var(--s-display);
  font-size: var(--s-step-0);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

/* ---------- Accessibility ---------- */

:focus-visible {
  outline: 2px solid var(--s-signal);
  outline-offset: 3px;
  border-radius: 2px;
}

.s-skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--s-signal);
  color: var(--s-void);
  padding: var(--s-3) var(--s-4);
  font-weight: 700;
  z-index: 100;
}
.s-skip:focus {
  left: var(--s-4);
  top: var(--s-4);
}

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

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
    scroll-behavior: auto !important;
  }
}

/* ---------- Layout ---------- */

.s-page {
  width: min(100% - 2.5rem, var(--s-page));
  margin-inline: auto;
}

.s-narrow {
  width: min(100% - 2.5rem, 72ch);
  margin-inline: auto;
}

.s-section {
  padding-block: var(--s-24);
  border-top: var(--s-rule);
}

/* Asymmetric split — deliberately not 50/50 (§5, frontend direction). */
.s-split {
  display: grid;
  gap: var(--s-12);
  grid-template-columns: 1fr;
}
@media (min-width: 60rem) {
  .s-split {
    grid-template-columns: 5fr 7fr;
    align-items: start;
  }
  .s-split--flip {
    grid-template-columns: 7fr 5fr;
  }
}

.s-stack > * + * {
  margin-top: var(--s-4);
}
.s-stack--lg > * + * {
  margin-top: var(--s-8);
}

/* ---------- Typography ---------- */

.s-display {
  font-size: var(--s-step-4);
  line-height: 0.92;
  letter-spacing: -0.045em;
  font-weight: 800;
  margin: 0;
  text-wrap: balance;
}

.s-h2 {
  font-size: var(--s-step-3);
  line-height: 1.0;
  letter-spacing: -0.035em;
  font-weight: 700;
  margin: 0;
  text-wrap: balance;
}

.s-h3 {
  font-size: var(--s-step-1);
  line-height: 1.2;
  letter-spacing: -0.015em;
  font-weight: 650;
  margin: 0;
}

.s-lede {
  font-size: var(--s-step-1);
  line-height: 1.5;
  color: var(--s-ink-mid);
  max-width: var(--s-measure);
  margin: 0;
  text-wrap: pretty;
}

.s-prose {
  max-width: var(--s-measure);
  color: var(--s-ink-mid);
}
.s-prose p,
.s-prose ul,
.s-prose ol {
  margin-block: var(--s-4);
}
.s-prose h2 {
  color: var(--s-ink);
  font-size: var(--s-step-2);
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-block: var(--s-12) var(--s-4);
}
.s-prose h3 {
  color: var(--s-ink);
  font-size: var(--s-step-1);
  letter-spacing: -0.015em;
  margin-block: var(--s-8) var(--s-3);
}
.s-prose strong {
  color: var(--s-ink);
  font-weight: 650;
}
.s-prose code {
  font-family: var(--s-mono);
  font-size: 0.9em;
  background: var(--s-surface);
  border: var(--s-rule);
  border-radius: var(--s-radius);
  padding: 0.1em 0.35em;
  color: var(--s-signal);
}
.s-prose a {
  color: var(--s-ink);
  text-decoration-color: var(--s-signal);
  text-underline-offset: 3px;
  text-decoration-thickness: 1px;
}
.s-prose a:hover {
  color: var(--s-signal);
}

/* The instrument label: small, tracked-out mono. Used everywhere. */
.s-label {
  font-family: var(--s-mono);
  font-size: var(--s-step--1);
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--s-ink-dim);
  margin: 0;
}

.s-mono {
  font-family: var(--s-mono);
  font-size: 0.92em;
}

/* ---------- Components ---------- */

.s-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  font-family: var(--s-mono);
  font-size: var(--s-step--1);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 600;
  padding: var(--s-3) var(--s-6);
  border-radius: var(--s-radius);
  border: 1px solid var(--s-signal);
  background: var(--s-signal);
  color: var(--s-void);
  text-decoration: none;
  cursor: pointer;
  transition: transform var(--s-dur) var(--s-ease), background var(--s-dur) var(--s-ease);
}
.s-btn:hover {
  transform: translateY(-2px);
  background: #6ee4f4;
}
.s-btn--ghost {
  background: transparent;
  color: var(--s-ink);
  border-color: var(--s-line-bright);
}
.s-btn--ghost:hover {
  background: var(--s-surface);
  border-color: var(--s-signal);
  color: var(--s-signal);
}

.s-card {
  background: var(--s-surface);
  border: var(--s-rule);
  border-radius: var(--s-radius-lg);
  padding: var(--s-6);
}

.s-grid {
  display: grid;
  gap: var(--s-4);
  grid-template-columns: repeat(auto-fit, minmax(min(100%, 17rem), 1fr));
}

/* Status pill — always pairs colour with a text label (§51). */
.s-pill {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  font-family: var(--s-mono);
  font-size: var(--s-step--1);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  padding: 0.15rem var(--s-2);
  border-radius: var(--s-radius);
  border: 1px solid currentColor;
  white-space: nowrap;
}
.s-pill::before {
  content: '';
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: currentColor;
  flex: none;
}
.s-pill--blocked { color: var(--s-stop); }
.s-pill--allowed { color: var(--s-ok); }
.s-pill--restricted { color: var(--s-warn); }
.s-pill--measured { color: var(--s-signal); }
.s-pill--unknown { color: var(--s-ink-dim); }

/* Confidence marker — Sessyn must never disguise inference as fact (§47). */
.s-confidence {
  font-family: var(--s-mono);
  font-size: var(--s-step--1);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--s-ink-dim);
  border-bottom: 1px dotted var(--s-line-bright);
  cursor: help;
}

/* ---------- Chrome ---------- */

.s-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  gap: var(--s-6);
  padding-block: var(--s-4);
  background: color-mix(in srgb, var(--s-base) 88%, transparent);
  backdrop-filter: blur(14px);
  border-bottom: var(--s-rule);
}
.s-nav__links {
  display: flex;
  gap: var(--s-4);
  margin-left: auto;
  flex-wrap: wrap;
}
.s-nav a {
  font-family: var(--s-mono);
  font-size: var(--s-step--1);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--s-ink-mid);
  text-decoration: none;
}
.s-nav a:hover,
.s-nav a[aria-current='page'] {
  color: var(--s-signal);
}

.s-wordmark {
  font-family: var(--s-mono);
  font-weight: 700;
  font-size: var(--s-step-0);
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--s-ink);
  text-decoration: none;
}
.s-wordmark span {
  color: var(--s-signal);
}

.s-footer {
  border-top: var(--s-rule);
  padding-block: var(--s-12);
  color: var(--s-ink-dim);
  font-size: var(--s-step--1);
}
.s-footer a {
  color: var(--s-ink-mid);
  text-decoration: none;
}
.s-footer a:hover {
  color: var(--s-signal);
}

/* ---------- Motion: one orchestrated page load, not scattered fidgets ---------- */

@keyframes s-rise {
  from {
    opacity: 0;
    transform: translateY(14px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}

.s-rise {
  animation: s-rise 700ms var(--s-ease) both;
}
.s-rise:nth-child(2) { animation-delay: 70ms; }
.s-rise:nth-child(3) { animation-delay: 140ms; }
.s-rise:nth-child(4) { animation-delay: 210ms; }

/* Scroll-triggered reveal, CSS-only where supported. */
@supports (animation-timeline: view()) {
  @media (prefers-reduced-motion: no-preference) {
    .s-reveal {
      animation: s-rise 1ms linear both;
      animation-timeline: view();
      animation-range: entry 5% cover 26%;
    }
  }
}