/* ============================================================
   Northsignal Research — styles.css
   Light "white-paper" institutional theme. No framework.
   ============================================================ */

:root {
  /* Color tokens */
  --bg: #ffffff;
  --surface: #f7f8fa;
  --surface-2: #f1f3f6;
  --text: #0b1220;
  --muted: #5b6675;
  --hairline: #e4e7ec;
  --accent: #13294b;
  --accent-hover: #1d3a66;
  --accent-tint: #eef2f8;

  /* Typography */
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-serif: "Source Serif 4", Georgia, "Times New Roman", serif;
  --font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, monospace;

  /* Layout */
  --maxw: 1120px;
  --pad: clamp(1.25rem, 4vw, 2.5rem);
  --radius: 8px;
  --section-y: clamp(3.5rem, 8vw, 6.5rem);
}

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

html { scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.6;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3 { line-height: 1.15; margin: 0; font-weight: 600; letter-spacing: -0.01em; }
p { margin: 0; }
a { color: inherit; text-decoration: none; }

.container {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--pad);
}

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: #fff;
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius) 0;
  z-index: 100;
}
.skip-link:focus { left: 0; }

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

/* ---------- Brand ---------- */
.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  color: var(--accent);
}
.brand-mark { display: block; flex: none; }
.brand-name {
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.12em;
  color: var(--text);
  display: inline-flex;
  align-items: baseline;
  gap: 0.4rem;
}
.brand-sub {
  font-weight: 500;
  font-size: 0.7rem;
  letter-spacing: 0.22em;
  color: var(--muted);
}

/* ---------- Header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: saturate(160%) blur(10px);
  border-bottom: 1px solid var(--hairline);
}
.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  min-height: 64px;
}
.nav-menu {
  display: flex;
  align-items: center;
  gap: 1.75rem;
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav-menu a {
  font-size: 0.92rem;
  font-weight: 500;
  color: var(--muted);
  transition: color 0.15s ease;
}
.nav-menu a:hover { color: var(--text); }
.nav-cta {
  color: var(--accent) !important;
  border: 1px solid var(--hairline);
  padding: 0.45rem 0.95rem;
  border-radius: var(--radius);
  transition: border-color 0.15s ease, background 0.15s ease;
}
.nav-cta:hover { border-color: var(--accent); background: var(--accent-tint); }

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 42px;
  height: 38px;
  padding: 9px 8px;
  background: none;
  border: 1px solid var(--hairline);
  border-radius: var(--radius);
  cursor: pointer;
}
.nav-toggle-bar {
  display: block;
  height: 2px;
  width: 100%;
  background: var(--text);
  transition: transform 0.2s ease, opacity 0.2s ease;
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.8rem 1.5rem;
  border-radius: var(--radius);
  border: 1px solid transparent;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, transform 0.05s ease;
}
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-hover); }
.btn-primary:active { transform: translateY(1px); }
.btn-ghost { background: transparent; color: var(--accent); border-color: var(--hairline); }
.btn-ghost:hover { border-color: var(--accent); background: var(--accent-tint); }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding-block: clamp(4rem, 10vw, 7.5rem) var(--section-y);
  background:
    radial-gradient(60% 60% at 50% 0%, var(--surface) 0%, transparent 70%),
    linear-gradient(180deg, #ffffff 0%, #ffffff 100%);
  border-bottom: 1px solid var(--hairline);
  overflow: hidden;
}
.hero::before {
  /* faint dot-grid texture */
  content: "";
  position: absolute;
  inset: 0;
  background-image: radial-gradient(var(--hairline) 1px, transparent 1px);
  background-size: 22px 22px;
  -webkit-mask-image: radial-gradient(70% 55% at 50% 12%, #000 0%, transparent 75%);
  mask-image: radial-gradient(70% 55% at 50% 12%, #000 0%, transparent 75%);
  opacity: 0.55;
  pointer-events: none;
}
.hero-inner { position: relative; max-width: 760px; }
.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1.1rem;
}
.hero-title {
  font-family: var(--font-serif);
  font-weight: 500;
  font-size: clamp(2.35rem, 6vw, 4rem);
  letter-spacing: -0.02em;
  line-height: 1.06;
  margin-bottom: 1.4rem;
}
.hero-sub {
  font-size: clamp(1.05rem, 2.2vw, 1.3rem);
  color: var(--muted);
  max-width: 60ch;
  margin-bottom: 2rem;
}
.hero-actions { display: flex; flex-wrap: wrap; gap: 0.9rem; margin-bottom: 1.6rem; }
.hero-meta {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.06em;
  color: var(--muted);
}

/* ---------- Sections ---------- */
.section { padding-block: var(--section-y); }
.section-alt { background: var(--surface); border-block: 1px solid var(--hairline); }
.section-head { max-width: 640px; margin-bottom: clamp(2rem, 5vw, 3.25rem); }
.section-label {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.85rem;
}
.section-title {
  font-size: clamp(1.7rem, 4vw, 2.4rem);
  margin-bottom: 0.9rem;
}
.section-lede { color: var(--muted); font-size: 1.08rem; }

/* ---------- Coverage cards ---------- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.1rem;
}
.card {
  background: var(--bg);
  border: 1px solid var(--hairline);
  border-radius: var(--radius);
  padding: 1.6rem 1.5rem;
  transition: border-color 0.18s ease, transform 0.18s ease, box-shadow 0.18s ease;
}
.section-alt .card { background: var(--bg); }
.card:hover {
  border-color: #cdd4df;
  transform: translateY(-2px);
  box-shadow: 0 8px 24px -16px rgba(11, 18, 32, 0.4);
}
.card-title { font-size: 1.12rem; margin-bottom: 0.6rem; }
.card-body { color: var(--muted); font-size: 0.97rem; }

/* ---------- Approach pillars ---------- */
.pillar-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: clamp(1.4rem, 4vw, 2.75rem);
}
.pillar { border-top: 2px solid var(--accent); padding-top: 1.25rem; }
.pillar-index {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--accent);
  letter-spacing: 0.05em;
}
.pillar-title { font-size: 1.25rem; margin: 0.5rem 0 0.6rem; }
.pillar-body { color: var(--muted); font-size: 0.99rem; }

/* ---------- About ---------- */
.about-grid {
  display: grid;
  grid-template-columns: 1.6fr 1fr;
  gap: clamp(2rem, 5vw, 4rem);
  align-items: start;
}
.about-copy .section-title { margin-bottom: 1.1rem; }
.about-body { color: var(--muted); margin-bottom: 1rem; max-width: 56ch; }
.about-aside {
  background: var(--surface);
  border: 1px solid var(--hairline);
  border-radius: var(--radius);
  padding: 1.6rem 1.5rem;
}
.aside-label {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 1rem;
}
.aside-list { list-style: none; margin: 0; padding: 0; }
.aside-list li {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.7rem 0;
  border-top: 1px solid var(--hairline);
  font-size: 0.95rem;
  text-align: right;
}
.aside-list li:first-child { border-top: none; }
.aside-list span { color: var(--muted); font-weight: 500; text-align: left; }

/* ---------- Contact ---------- */
.contact-inner { max-width: 680px; }
.contact-lede { color: var(--muted); font-size: 1.1rem; margin-bottom: 1.8rem; }
.contact-email {
  display: inline-block;
  font-family: var(--font-serif);
  font-size: clamp(1.4rem, 4vw, 2.1rem);
  font-weight: 500;
  color: var(--accent);
  border-bottom: 2px solid var(--accent-tint);
  padding-bottom: 0.2rem;
  transition: border-color 0.18s ease;
  word-break: break-word;
}
.contact-email:hover { border-color: var(--accent); }
.contact-note {
  margin-top: 1.4rem;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--muted);
}

/* ---------- Footer ---------- */
.site-footer {
  background: var(--text);
  color: #c7cdd8;
  padding-block: clamp(2.5rem, 6vw, 4rem) 2rem;
}
.footer-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  align-items: center;
  gap: 1.5rem;
  padding-bottom: 2rem;
  margin-bottom: 2rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}
.site-footer .brand-name { color: #fff; }
.site-footer .brand-sub { color: #8b95a6; }
.site-footer .brand { color: #fff; }
.footer-tagline { margin-top: 0.6rem; font-size: 0.9rem; color: #8b95a6; }
.footer-meta a {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: #c7cdd8;
  border-bottom: 1px solid rgba(255, 255, 255, 0.2);
  padding-bottom: 2px;
  transition: color 0.15s ease;
}
.footer-meta a:hover { color: #fff; }
.disclaimer {
  font-size: 0.8rem;
  line-height: 1.65;
  color: #8b95a6;
  max-width: 78ch;
  margin-bottom: 1.25rem;
}
.copyright { font-size: 0.82rem; color: #8b95a6; }

/* ---------- Responsive ---------- */
@media (max-width: 760px) {
  .nav-toggle { display: flex; }
  .nav-menu {
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--hairline);
    padding: 0.5rem var(--pad) 1rem;
    box-shadow: 0 12px 24px -18px rgba(11, 18, 32, 0.5);
    display: none;
  }
  .nav-menu.open { display: flex; }
  .nav-menu li { width: 100%; }
  .nav-menu a { display: block; padding: 0.85rem 0; font-size: 1rem; }
  .nav-cta { text-align: center; margin-top: 0.5rem; }
  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) { transform: translateY(7px) rotate(45deg); }
  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(2) { opacity: 0; }
  .nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

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