/* ==============================================
   psychonetrics Website — Design System
   NUS Identity: Blue #003D7C, Orange #EF7C00
   ============================================== */

/* --- Custom Properties --- */
:root {
  --nus-blue: #003D7C;
  --nus-blue-dark: #002D5C;
  --nus-blue-light: #E8EEF5;
  --nus-orange: #EF7C00;
  --nus-orange-light: #F1991F;
  --nus-orange-dark: #AB3E24;

  --white: #FFFFFF;
  --gray-50: #F9FAFB;
  --gray-100: #F3F4F6;
  --gray-200: #E5E7EB;
  --gray-300: #D1D5DB;
  --gray-500: #6B7280;
  --gray-600: #4B5563;
  --gray-700: #374151;
  --gray-800: #1F2937;
  --gray-900: #111827;

  --code-bg: #F8F9FA;
  --code-text: #2D3748;
  --code-border: #E2E8F0;

  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'Fira Code', 'Source Code Pro', 'Consolas', monospace;

  --max-w: 1200px;
  --max-w-narrow: 860px;
}

/* --- Reset & Base --- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { font-size: 16px; scroll-behavior: smooth; scroll-padding-top: 80px; }

body {
  font-family: var(--font-body);
  font-size: 1.05rem;
  line-height: 1.7;
  color: var(--gray-700);
  background: var(--gray-50);
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-body);
  color: var(--gray-900);
  font-weight: 700;
  line-height: 1.3;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
}
h1 { font-size: 2.5rem; margin-top: 0; }
h2 { font-size: 1.9rem; border-bottom: 2px solid var(--nus-blue-light); padding-bottom: .4rem; }
h3 { font-size: 1.45rem; }
h4 { font-size: 1.15rem; }

p { margin-bottom: 1rem; }

a { color: var(--nus-orange); text-decoration: none; transition: color .2s; }
a:hover { color: var(--nus-orange-dark); text-decoration: underline; }

strong { color: var(--gray-900); }

ul, ol { margin-bottom: 1rem; padding-left: 1.5rem; }
li { margin-bottom: .35rem; }

/* --- Layout --- */
.container { width: 100%; max-width: var(--max-w); margin: 0 auto; padding: 0 1.5rem; }
.container-narrow { max-width: var(--max-w-narrow); }
.section { padding: 4rem 0; }

/* --- Navigation --- */
.navbar {
  position: sticky; top: 0; z-index: 1000;
  background: var(--nus-blue);
  box-shadow: 0 2px 8px rgba(0,0,0,.12);
}
.nav-container {
  display: flex; justify-content: space-between; align-items: center;
  padding: .6rem 0;
}
.nav-brand {
  font-weight: 700; font-size: 1.25rem; color: var(--white);
  font-family: var(--font-mono); letter-spacing: -.5px;
  text-decoration: none;
}
.nav-brand:hover { color: var(--nus-orange); text-decoration: none; }
.nav-menu { display: flex; list-style: none; gap: .25rem; align-items: center; margin: 0; padding: 0; }
.nav-link {
  display: block; padding: .5rem .85rem; color: rgba(255,255,255,.88);
  border-radius: 6px; transition: background .2s, color .2s;
  font-size: .92rem; font-weight: 500; text-decoration: none;
}
.nav-link:hover, .nav-link.active {
  background: var(--nus-orange); color: var(--white); text-decoration: none;
}
.nav-toggle {
  display: none; background: none; border: none; color: var(--white);
  font-size: 1.6rem; cursor: pointer; padding: .25rem;
}

/* --- Dropdown Menu --- */
.nav-dropdown { position: relative; }
.dropdown-toggle {
  font-family: inherit; cursor: pointer; border: none; background: none;
  display: flex; align-items: center; gap: .35rem;
}
.dropdown-chevron { transition: transform .2s; flex-shrink: 0; }
.nav-dropdown.open .dropdown-chevron { transform: rotate(180deg); }
.dropdown-menu {
  display: none; position: absolute; top: 100%; left: 0;
  min-width: 160px; background: var(--nus-blue-dark);
  border-radius: 0 0 8px 8px; box-shadow: 0 8px 24px rgba(0,0,0,.2);
  list-style: none; padding: .35rem 0; margin: 0; z-index: 1001;
}
.nav-dropdown.open .dropdown-menu { display: block; }
.dropdown-menu .nav-link {
  display: block; padding: .5rem 1rem; border-radius: 0;
  white-space: nowrap; font-size: .88rem;
}
.dropdown-menu .nav-link:hover,
.dropdown-menu .nav-link.active {
  background: var(--nus-orange); color: var(--white);
}
.dropdown-toggle.parent-active {
  background: rgba(239,124,0,.25); color: var(--white);
}

/* --- Hero --- */
.hero {
  text-align: center;
  padding: 3rem 0 2rem;
}
.hero h1 { font-size: 2.8rem; margin-bottom: .5rem; }
.hero .tagline {
  font-size: 1.25rem; color: var(--gray-500); margin-bottom: 2rem; font-weight: 400;
}
/* --- Logo (SVG) + hero layout --- */
.hero-logo-wrap {
  max-width: var(--max-w-narrow);
  margin: 0 auto;
  position: relative;
}
.logo-svg {
  display: block;
  width: 100%;
  height: auto;
}
.hero-buttons {
  display: flex; gap: .75rem; flex-wrap: wrap;
  justify-content: flex-start;
  position: relative;
  margin-top: -2.5rem;
  padding-left: 28%;
}

/* --- ASCII Logo (fallback, used on other pages if needed) --- */
.logo-ascii {
  font-family: var(--font-mono);
  color: var(--nus-blue);
  font-size: clamp(.45rem, .72vw, .72rem);
  line-height: 1.15;
  white-space: pre;
  overflow-x: auto;
  padding: 1.2rem 1.5rem;
  background: var(--nus-blue-light);
  border-left: 4px solid var(--nus-orange);
  border-radius: 0 6px 6px 0;
  margin: 1.5rem auto;
  max-width: 720px;
  text-align: left;
}

/* --- Buttons --- */
.btn {
  display: inline-block; padding: .65rem 1.5rem; border-radius: 6px;
  font-weight: 600; font-size: .95rem; text-align: center;
  transition: background .2s, transform .1s, box-shadow .2s;
  cursor: pointer; border: none; text-decoration: none;
}
.btn:hover { transform: translateY(-1px); text-decoration: none; }
.btn-primary { background: var(--nus-orange); color: var(--white); }
.btn-primary:hover { background: var(--nus-orange-light); color: var(--white); box-shadow: 0 4px 12px rgba(239,124,0,.3); }
.btn-secondary { background: var(--white); color: var(--nus-blue); border: 2px solid var(--nus-blue); }
.btn-secondary:hover { background: var(--nus-blue-light); }
.btn-sm { padding: .4rem 1rem; font-size: .85rem; }

/* --- Cards --- */
.card {
  background: var(--white); border-radius: 12px; padding: 2rem;
  box-shadow: 0 1px 3px rgba(0,0,0,.08); transition: box-shadow .3s, transform .3s;
}
.card:hover { box-shadow: 0 6px 20px rgba(0,61,124,.12); transform: translateY(-3px); }
.card h3 { margin-top: 0; color: var(--nus-blue); }
.card p { color: var(--gray-600); }
.card .card-link {
  display: inline-block; margin-top: .75rem; font-weight: 600; color: var(--nus-orange);
}
.cards-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem; margin: 2rem 0;
}

/* --- Feature Grid --- */
.feature-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 1.25rem; margin: 2rem 0;
}
.feature-item {
  padding: 1.25rem; border-radius: 8px; background: var(--white);
  border: 1px solid var(--gray-200);
}
.feature-item h4 { margin-top: 0; color: var(--nus-blue); font-size: 1.05rem; }
.feature-item p { margin-bottom: 0; font-size: .93rem; color: var(--gray-600); }

/* --- Code Blocks --- */
pre[class*="language-"] {
  background: var(--code-bg) !important;
  border: 1px solid var(--code-border);
  border-radius: 8px;
  padding: 1.25rem 1.5rem;
  overflow-x: auto;
  font-size: .88rem;
  line-height: 1.65;
  margin: 1.5rem 0;
  position: relative;
}
code[class*="language-"] {
  font-family: var(--font-mono) !important;
}

/* Inline code */
:not(pre) > code {
  font-family: var(--font-mono);
  background: var(--nus-blue-light);
  padding: .15em .4em;
  border-radius: 4px;
  font-size: .88em;
  color: var(--nus-blue);
}

/* Copy button */
.copy-btn {
  position: absolute; top: .5rem; right: .5rem;
  background: var(--gray-200); border: none; border-radius: 4px;
  padding: .3rem .65rem; font-size: .78rem; color: var(--gray-600);
  cursor: pointer; transition: background .2s, color .2s;
  font-family: var(--font-body);
}
.copy-btn:hover { background: var(--nus-orange); color: var(--white); }
.copy-btn.copied { background: #059669; color: var(--white); }

/* --- Tables --- */
table {
  width: 100%; border-collapse: collapse;
  margin: 1.5rem 0; background: var(--white);
  border-radius: 8px; overflow: hidden;
  box-shadow: 0 1px 3px rgba(0,0,0,.08);
  font-size: .93rem;
}
thead { background: var(--nus-blue); color: var(--white); }
th { padding: .75rem 1rem; text-align: left; font-weight: 600; }
td { padding: .65rem 1rem; border-bottom: 1px solid var(--gray-200); }
tbody tr:last-child td { border-bottom: none; }
tbody tr:hover { background: var(--gray-50); }
td code { background: rgba(0,61,124,.07); color: var(--nus-blue-dark); padding: .1em .35em; border-radius: 3px; font-size: .88em; }

/* --- Math (KaTeX) --- */
.katex-display { margin: 1.5rem 0; overflow-x: auto; overflow-y: hidden; }
.katex { font-size: 1.1em; }

/* --- Info / Note boxes --- */
.note {
  padding: 1rem 1.25rem; border-radius: 8px; margin: 1.5rem 0;
  border-left: 4px solid var(--nus-blue); background: var(--nus-blue-light);
  font-size: .95rem;
}
.note strong { color: var(--nus-blue); }
.warning {
  padding: 1rem 1.25rem; border-radius: 8px; margin: 1.5rem 0;
  border-left: 4px solid var(--nus-orange); background: #FFF7ED;
  font-size: .95rem;
}

/* --- Table of Contents --- */
.toc {
  background: var(--white); border: 1px solid var(--gray-200); border-radius: 8px;
  padding: 1.25rem 1.5rem; margin: 2rem 0;
}
.toc h4 { margin-top: 0; color: var(--nus-blue); font-size: 1rem; }
.toc ol { margin-bottom: 0; }
.toc li { font-size: .93rem; }
.toc a { color: var(--nus-blue); }
.toc a:hover { color: var(--nus-orange); }

/* --- Example cards (examples page) --- */
.example-card {
  background: var(--white); border-radius: 10px;
  box-shadow: 0 1px 3px rgba(0,0,0,.08);
  overflow: hidden; margin-bottom: 1.5rem;
}
.example-header {
  padding: 1.25rem 1.5rem; cursor: pointer;
  display: flex; justify-content: space-between; align-items: center;
  transition: background .2s;
}
.example-header:hover { background: var(--gray-50); }
.example-header h3 { margin: 0; font-size: 1.1rem; }
.example-tag {
  display: inline-block; padding: .15rem .55rem; border-radius: 12px;
  font-size: .75rem; font-weight: 600; margin-left: .5rem;
}
.tag-varcov { background: #DBEAFE; color: #1E40AF; }
.tag-lvm { background: #D1FAE5; color: #065F46; }
.tag-ising { background: #FEE2E2; color: #991B1B; }
.tag-var1 { background: #FEF3C7; color: #92400E; }
.tag-dlvm1 { background: #E0E7FF; color: #3730A3; }
.tag-general { background: #E5E7EB; color: #374151; }
.example-meta { font-size: .88rem; color: var(--gray-500); margin-top: .25rem; }
.example-body { display: none; padding: 0 1.5rem 1.5rem; border-top: 1px solid var(--gray-200); }
.example-body.open { display: block; }
.example-chevron { transition: transform .3s; font-size: 1.2rem; color: var(--gray-400); }
.example-chevron.open { transform: rotate(180deg); }

/* --- Author Card (about page) --- */
.author-card {
  display: flex; gap: 2rem; align-items: flex-start;
  background: var(--white); border-radius: 12px; padding: 2rem;
  box-shadow: 0 1px 3px rgba(0,0,0,.08); margin: 1.5rem 0;
}
.author-photo { flex-shrink: 0; }
.author-photo img {
  width: 180px; height: auto; border-radius: 8px;
  border: 4px solid var(--nus-blue-light);
}
.author-info h3 { margin-top: 0; }

/* --- Footer --- */
footer {
  background: var(--gray-900); color: var(--gray-300); padding: 3.5rem 0 2rem;
  margin-top: 5rem; font-size: .93rem;
}
footer h4 { color: var(--white); font-size: 1.05rem; margin-top: 0; margin-bottom: .75rem; }
footer a { color: var(--nus-orange); }
footer a:hover { color: var(--nus-orange-light); }
footer ul { list-style: none; padding: 0; }
footer li { margin-bottom: .4rem; }
.footer-grid {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 2rem;
}
.footer-bottom {
  margin-top: 2.5rem; padding-top: 1.5rem; border-top: 1px solid var(--gray-700);
  text-align: center; color: var(--gray-500); font-size: .85rem;
}
.nus-logo-footer { max-width: 180px; height: auto; margin-top: .5rem; }

/* --- Page header (for tutorial pages) --- */
.page-header {
  padding: 2.5rem 0 1.5rem; border-bottom: 1px solid var(--gray-200);
  margin-bottom: 2rem;
}
.page-header h1 { margin-bottom: .5rem; }
.page-header .subtitle { font-size: 1.15rem; color: var(--gray-500); margin-bottom: 0; }

/* --- Responsive --- */
@media (max-width: 768px) {
  .nav-toggle { display: block; }
  .nav-menu {
    display: none; position: absolute; top: 100%; left: 0; right: 0;
    background: var(--nus-blue); flex-direction: column; padding: .75rem 1rem;
    box-shadow: 0 4px 12px rgba(0,0,0,.15);
  }
  .nav-menu.open { display: flex; }
  .nav-dropdown { position: static; }
  .dropdown-menu {
    position: static; background: rgba(0,0,0,.15);
    box-shadow: none; border-radius: 6px;
    margin: .25rem 0 .25rem .5rem; padding: .25rem 0;
  }
  .dropdown-menu .nav-link { padding: .45rem 1rem .45rem 1.5rem; font-size: .88rem; }
  h1 { font-size: 2rem; }
  h2 { font-size: 1.5rem; }
  .hero h1 { font-size: 2rem; }
  .hero .tagline { font-size: 1.05rem; }
  .section { padding: 2.5rem 0; }
  .cards-grid { grid-template-columns: 1fr; }
  .feature-grid { grid-template-columns: 1fr; }
  .logo-ascii { font-size: .38rem; padding: .75rem 1rem; }
  pre[class*="language-"] { font-size: .82rem; padding: 1rem; }
  .author-card { flex-direction: column; align-items: center; text-align: center; }
  .author-photo img { width: 140px; }
}

@media (max-width: 600px) {
  .logo-ascii { display: none; }
  .hero-buttons {
    margin-top: .75rem;
    padding-left: 0;
    justify-content: center;
  }
}
@media (max-width: 480px) {
  .hero-buttons { flex-direction: column; align-items: center; }
}