/* ==========================================================================
   iViRTH Center of Excellence & Innovation Center
   main.css — shared design system
   Tokens: ink #0A0A0A / paper #FFFFFF / paper-dim #F5F4F1 / line #DEDDD9 / mid #6E6D68
   Type: DM Sans (display + body) / DM Mono (system readouts, IDs, data)
   ========================================================================== */

:root{
  --ink:        #0A0A0A;
  --ink-soft:   #1C1C1A;
  --paper:      #FFFFFF;
  --paper-dim:  #F5F4F1;
  --line:       #DEDDD9;
  --line-strong:#B9B7B0;
  --mid:        #6E6D68;

  --font-display: 'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-body:    'DM Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono:    'DM Mono', 'SFMono-Regular', Consolas, monospace;

  --max-w: 1180px;
  --gutter: clamp(1.25rem, 4vw, 3rem);
  --radius: 2px;

  --ease: cubic-bezier(.2,.7,.2,1);
}

@media (prefers-color-scheme: dark){
  /* Reserved for future dark theme; site ships light-by-default for now. */
}

*,*::before,*::after{ box-sizing: border-box; }
html{ -webkit-text-size-adjust:100%; scroll-behavior:smooth; }
@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; }
}

body{
  margin:0;
  font-family: var(--font-body);
  color: var(--ink);
  background: var(--paper);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

img{ max-width:100%; display:block; }
a{ color: var(--ink); text-decoration: none; }
ul{ margin:0; padding:0; list-style:none; }
button{ font-family: inherit; }

h1,h2,h3,h4{
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.08;
  margin: 0 0 0.5em;
  letter-spacing: -0.01em;
}
h1{ font-size: clamp(2.1rem, 5.4vw, 3.8rem); }
h2{ font-size: clamp(1.6rem, 3.4vw, 2.4rem); }
h3{ font-size: clamp(1.15rem, 2vw, 1.45rem); }
p{ margin: 0 0 1em; color: var(--ink-soft); }

.lede{ font-size: clamp(1.05rem, 1.6vw, 1.25rem); color: var(--mid); max-width: 46em; }

.mono{ font-family: var(--font-mono); letter-spacing: 0.02em; }
.eyebrow{
  font-family: var(--font-mono);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--mid);
  display:flex;
  align-items:center;
  gap:0.5em;
  margin-bottom: 0.9em;
}
.eyebrow .zero{
  width: 0.9em; height: 0.9em; border:1.5px solid currentColor; border-radius:50%;
  display:inline-block;
}

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

.wrap{
  max-width: var(--max-w);
  margin: 0 auto;
  padding-left: var(--gutter);
  padding-right: var(--gutter);
}

.section{ padding: clamp(3rem, 7vw, 6rem) 0; }
.section--tight{ padding: clamp(2rem, 4vw, 3.25rem) 0; }
.section--dim{ background: var(--paper-dim); }
.section--ink{ background: var(--ink); color: var(--paper); }
.section--ink h1,.section--ink h2,.section--ink h3{ color: var(--paper); }
.section--ink p{ color: #C9C8C2; }
.section--ink .eyebrow{ color: #9C9B95; }
.rule-top{ border-top: 1px solid var(--line); }
.rule-bottom{ border-bottom: 1px solid var(--line); }

/* ---------- Dot-grid texture (ViSET terminal-grid motif) ---------- */
.grid-texture{
  position:relative;
  background-image:
    radial-gradient(circle, var(--line-strong) 1px, transparent 1.3px);
  background-size: 26px 26px;
  background-position: -4px -4px;
}
.section--ink.grid-texture{
  background-image: radial-gradient(circle, #3A3A37 1px, transparent 1.3px);
}

/* ---------- Buttons ---------- */
.btn{
  display:inline-flex; align-items:center; justify-content:center; gap:0.5em;
  font-family: var(--font-display);
  font-weight:600;
  font-size:0.95rem;
  padding: 0.85em 1.5em;
  border:1.5px solid var(--ink);
  border-radius: var(--radius);
  cursor:pointer;
  transition: background .18s var(--ease), color .18s var(--ease), transform .12s var(--ease);
  white-space:nowrap;
}
.btn--primary{ background: var(--ink); color: var(--paper); }
.btn--primary:hover{ background: var(--ink-soft); }
.btn--ghost{ background: transparent; color: var(--ink); }
.btn--ghost:hover{ background: var(--ink); color: var(--paper); }
.btn--on-ink{ border-color: var(--paper); color: var(--paper); }
.btn--on-ink:hover{ background: var(--paper); color: var(--ink); }
.btn:active{ transform: translateY(1px); }
.btn-row{ display:flex; gap:0.85rem; flex-wrap:wrap; align-items:center; }

/* ---------- Header / Nav ---------- */
.site-header{
  position: sticky; top:0; z-index: 60;
  background: rgba(255,255,255,0.92);
  backdrop-filter: saturate(140%) blur(8px);
  border-bottom: 1px solid var(--line);
}
.site-header .wrap{ display:flex; align-items:center; justify-content:space-between; height:72px; }
.brand{ display:flex; align-items:center; gap:0.55rem; font-family: var(--font-display); font-weight:700; font-size:1.15rem; }
.brand .zero-mark{
  width:1.3em; height:1.3em; border-radius:50%; border:2px solid var(--ink);
  display:inline-flex; align-items:center; justify-content:center;
  font-family: var(--font-mono); font-size:0.62em; font-weight:600;
}
.brand small{ display:block; font-family: var(--font-mono); font-size:0.6rem; color:var(--mid); letter-spacing:0.08em; text-transform:uppercase; font-weight:500; }

.main-nav{ display:flex; align-items:center; gap:1.6rem; }
.main-nav a{ font-size:0.92rem; font-weight:500; color: var(--ink-soft); padding:0.3rem 0; border-bottom:2px solid transparent; }
.main-nav a:hover, .main-nav a.is-active{ border-color: var(--ink); color:var(--ink); }
.nav-cta{ display:flex; align-items:center; gap:0.75rem; }

.nav-toggle{
  display:none; width:42px; height:42px; border:1.5px solid var(--ink); border-radius:var(--radius);
  background:transparent; align-items:center; justify-content:center; flex-direction:column; gap:4px;
}
.nav-toggle span{ width:18px; height:1.5px; background:var(--ink); display:block; }

.sticky-cta-banner{
  background: var(--ink); color: var(--paper);
  font-family: var(--font-mono);
  font-size: 0.82rem;
  text-align:center;
  padding: 0.55rem var(--gutter);
}
.sticky-cta-banner a{ color:var(--paper); text-decoration:underline; text-underline-offset:3px; }

@media (max-width: 880px){
  .main-nav{
    position:fixed; inset: 72px 0 0 0; background: var(--paper);
    flex-direction:column; align-items:flex-start; gap:0; padding: 1rem var(--gutter);
    transform: translateY(-8px); opacity:0; pointer-events:none; transition: all .2s var(--ease);
    border-top:1px solid var(--line);
  }
  .main-nav.is-open{ opacity:1; transform:none; pointer-events:auto; }
  .main-nav a{ width:100%; padding:0.95rem 0; border-bottom:1px solid var(--line); }
  .nav-cta{ display:none; }
  .main-nav.is-open .nav-cta{ display:flex; width:100%; padding-top:1rem; }
  .nav-toggle{ display:flex; }
}

/* ---------- Hero ---------- */
.hero{ padding: clamp(2.5rem, 8vw, 6rem) 0 clamp(2rem,5vw,4rem); }
.hero-head{ max-width: 52em; }
.hero-stats{
  display:grid; grid-template-columns: repeat(3,1fr); gap:1.5rem; margin-top: 2.5rem;
  border-top:1px solid var(--line); padding-top:1.75rem;
}
.hero-stats .stat-num{ font-family: var(--font-mono); font-size:1.6rem; font-weight:600; }
.hero-stats .stat-label{ font-size:0.82rem; color:var(--mid); margin-top:0.2rem; }
@media (max-width:680px){ .hero-stats{ grid-template-columns: 1fr 1fr; } }

/* ---------- Cards / grids ---------- */
.grid{ display:grid; gap: 1.5rem; }
.grid--2{ grid-template-columns: repeat(2, 1fr); }
.grid--3{ grid-template-columns: repeat(3, 1fr); }
.grid--4{ grid-template-columns: repeat(4, 1fr); }
@media (max-width: 920px){ .grid--3{ grid-template-columns: 1fr 1fr; } .grid--4{ grid-template-columns: 1fr 1fr; } }
@media (max-width: 640px){ .grid--2,.grid--3,.grid--4{ grid-template-columns: 1fr; } }

.card{
  border:1px solid var(--line); border-radius: var(--radius); padding: 1.75rem;
  background: var(--paper);
  transition: border-color .18s var(--ease), transform .18s var(--ease);
}
.card:hover{ border-color: var(--line-strong); }
.card-id{ font-family: var(--font-mono); font-size:0.78rem; color:var(--mid); margin-bottom:0.6rem; display:block; }

.node-card{ border:1px solid var(--line); padding:2rem; border-radius:var(--radius); }
.node-card .node-tag{ font-family:var(--font-mono); font-size:0.8rem; color:var(--mid); }

.tier-card{ border:1px solid var(--line); border-radius:var(--radius); padding:2rem; position:relative; }
.tier-card .tier-num{ font-family: var(--font-mono); font-size:0.85rem; color:var(--mid); }
.tier-card ul{ margin-top:1rem; display:grid; gap:0.55rem; }
.tier-card li{ padding-left:1.1em; position:relative; font-size:0.93rem; color: var(--ink-soft); }
.tier-card li::before{ content:'—'; position:absolute; left:0; color:var(--mid); }
.tier-card.is-core{ background: var(--ink); color: var(--paper); border-color: var(--ink); }
.tier-card.is-core p,.tier-card.is-core li,.tier-card.is-core .tier-num{ color:#CFCEC8; }
.tier-card.is-core li::before{ color:#8B8A85; }

/* ---------- Challenge / status chips ---------- */
.chip{
  display:inline-flex; align-items:center; gap:0.4em;
  font-family: var(--font-mono); font-size:0.74rem; text-transform:uppercase; letter-spacing:0.08em;
  padding:0.3em 0.7em; border:1px solid var(--ink); border-radius: 20px;
}
.chip--live{ background: var(--ink); color: var(--paper); }
.chip--live::before{ content:''; width:6px; height:6px; border-radius:50%; background: var(--paper); animation: pulse 1.6s infinite; }
@keyframes pulse{ 0%,100%{opacity:1;} 50%{opacity:.25;} }

/* ---------- Formula / validation readout ---------- */
.readout{
  font-family: var(--font-mono);
  background: var(--ink); color: var(--paper);
  border-radius: var(--radius);
  padding: 1.75rem 2rem;
  font-size: clamp(1rem, 2vw, 1.3rem);
  overflow-x:auto;
  display:flex; align-items:center; gap:1rem;
}
.readout .lambda{ color:#9C9B95; }

/* ---------- Forms ---------- */
.form-grid{ display:grid; gap:1.4rem; }
.field{ display:flex; flex-direction:column; gap:0.45rem; }
.field label{ font-size:0.86rem; font-weight:600; }
.field .hint{ font-size:0.8rem; color:var(--mid); margin-top:-0.2rem; }
.field input,.field select,.field textarea{
  font-family: var(--font-body); font-size:0.96rem;
  border:1.5px solid var(--line-strong); border-radius: var(--radius);
  padding: 0.75em 0.9em; background: var(--paper); color: var(--ink);
}
.field input:focus,.field select:focus,.field textarea:focus{ border-color: var(--ink); outline:none; }
.field textarea{ resize: vertical; min-height: 110px; }
.checkbox-field{ display:flex; align-items:flex-start; gap:0.65rem; }
.checkbox-field input{ margin-top:0.25rem; width:auto; }
.checkbox-field label{ font-weight:400; font-size:0.9rem; }
.form-card{ border:1px solid var(--line); border-radius: var(--radius); padding: clamp(1.5rem,4vw,2.75rem); background: var(--paper-dim); }
.form-msg{ padding:0.9rem 1.1rem; border-radius:var(--radius); font-size:0.9rem; margin-bottom:1.25rem; }
.form-msg--success{ background:#0A0A0A; color:#fff; }
.form-msg--error{ background:#fff; border:1.5px solid var(--ink); }

/* ---------- Table ---------- */
.table-wrap{ overflow-x:auto; }
table{ width:100%; border-collapse:collapse; font-size:0.92rem; }
th,td{ text-align:left; padding:0.85rem 1rem; border-bottom:1px solid var(--line); }
th{ font-family: var(--font-mono); font-size:0.74rem; text-transform:uppercase; letter-spacing:0.06em; color:var(--mid); }

/* ---------- Footer ---------- */
.site-footer{ background: var(--ink); color:#D8D7D2; padding: 3rem 0 1.5rem; }
.site-footer a{ color:#D8D7D2; }
.site-footer a:hover{ color:#fff; text-decoration:underline; }
.footer-grid{ display:grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap:2rem; padding-bottom:2.5rem; border-bottom:1px solid #2B2B28; }
.footer-grid h4{ color:#fff; font-size:0.85rem; text-transform:uppercase; letter-spacing:0.08em; margin-bottom:1rem; font-family:var(--font-mono); }
.footer-grid li{ margin-bottom:0.6rem; font-size:0.9rem; }
.footer-bottom{ display:flex; flex-wrap:wrap; gap:1rem; justify-content:space-between; padding-top:1.5rem; font-size:0.8rem; color:#9C9B95; font-family: var(--font-mono); }
@media (max-width:880px){ .footer-grid{ grid-template-columns: 1fr 1fr; } }
@media (max-width:560px){ .footer-grid{ grid-template-columns: 1fr; } }

/* ---------- Utilities ---------- */
.flow > * + *{ margin-top:1rem; }
.center{ text-align:center; }
.mt-0{ margin-top:0 !important; }
.divider{ border:none; border-top:1px solid var(--line); margin: 2.5rem 0; }
.skip-link{ position:absolute; left:-9999px; }
.skip-link:focus{ left: 1rem; top:1rem; background:var(--ink); color:var(--paper); padding:0.5rem 1rem; z-index:100; }