/* ============================================================
   Shantanu Singh — portfolio styles
   Refactored from the original single-file build.
   Same dark SOC/terminal identity, refined for contrast,
   spacing, keyboard focus, and reduced-motion.
   No third-party fonts, no external assets.
============================================================ */

/* ============================================================
   DESIGN TOKENS — change here to retheme everything
============================================================ */
:root {
  --bg:          #080b0f;
  --bg-card:     #0d1117;
  --bg-elevated: #131920;
  --border:      #1c2432;
  --border-hi:   #263042;
  --text:        #cdd5e0;
  --text-2:      #97afca;   /* lifted slightly for readability */
  --text-3:      #6f8baa;   /* lifted from #5a7a99 to clear contrast on near-black */
  --accent:      #00d4a0;
  --accent-dim:  #00855e;
  --info:        #fdba74;   /* keywords/dates — amber, same as the hero terminal's string values */
  --font-mono:   ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, 'Liberation Mono', 'Courier New', monospace;
  --font-sans:   system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --radius:      5px;
  --radius-lg:   9px;
  --max-w:       940px;
}

/* ============================================================
   RESET
============================================================ */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; color-scheme: dark; }
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.7;
  font-weight: 400;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
ul { list-style: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }

/* Visible keyboard focus everywhere interactive */
a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 2px;
}

/* Skip link for keyboard / screen-reader users */
.skip-link {
  position: absolute;
  left: -999px;
  top: 8px;
  z-index: 200;
  background: var(--accent);
  color: var(--bg);
  font-family: var(--font-mono);
  font-size: .74rem;
  padding: 8px 14px;
  border-radius: var(--radius);
}
.skip-link:focus {
  left: 12px;
  text-decoration: none;
}

/* ============================================================
   SCAN-LINE TEXTURE (pure CSS, no external image) — dialed down
============================================================ */
body::after {
  content: '';
  position: fixed;
  inset: 0;
  background: repeating-linear-gradient(
    0deg,
    transparent,
    transparent 2px,
    rgba(0, 0, 0, .035) 2px,
    rgba(0, 0, 0, .035) 4px
  );
  pointer-events: none;
  z-index: 999;
}

/* ============================================================
   LAYOUT
============================================================ */
.wrap { max-width: var(--max-w); margin: 0 auto; padding: 0 20px; }

/* ============================================================
   NAV
============================================================ */
nav {
  position: fixed; top: 0; left: 0; right: 0;
  z-index: 100;
  background: rgba(8, 11, 15, .88);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 54px;
}
.nav-links {
  display: flex;
  gap: 24px;
  align-items: center;
}
.nav-links a {
  font-family: var(--font-mono);
  font-size: .72rem;
  color: var(--text-2);
  letter-spacing: .06em;
  text-transform: uppercase;
  transition: color .15s;
}
.nav-links a:hover,
.nav-links a.active { color: var(--accent); text-decoration: none; }

/* Hamburger / cross toggle — hidden on desktop, shown at the mobile
   breakpoint below where the full link list no longer fits. */
.nav-toggle {
  display: none;
  width: 26px;
  height: 20px;
  flex-direction: column;
  justify-content: space-between;
  background: none;
  border: none;
  padding: 0;
  z-index: 101;
}
.nav-toggle-bar {
  display: block;
  width: 100%;
  height: 2px;
  border-radius: 2px;
  background: var(--text);
  transition: transform .25s ease, opacity .2s ease;
}
.nav-toggle[aria-expanded="true"] .nav-toggle-bar:nth-child(1) {
  transform: translateY(9px) 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(-9px) rotate(-45deg);
}

/* ============================================================
   SECTIONS
============================================================ */
section {
  padding: 88px 0 64px;
  scroll-margin-top: 64px;   /* keep titles clear of the fixed nav on anchor jumps */
}
.sec-label {
  font-family: var(--font-mono);
  font-size: .68rem;
  color: var(--accent);
  letter-spacing: .14em;
  text-transform: uppercase;
  margin-bottom: 4px;
  text-align: center;
}
.sec-title {
  font-size: 1.6rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 40px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
  line-height: 1.2;
  letter-spacing: -.005em;
  text-align: center;
}

/* ============================================================
   HERO
============================================================ */
#hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: 54px;
}
.hero-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 56px;
  align-items: center;
}
.hero-greeting {
  font-family: var(--font-mono);
  font-size: .82rem;
  color: var(--text-2);
  letter-spacing: .04em;
  margin-bottom: 6px;
}
.hero-name {
  font-size: clamp(2rem, 4.5vw, 3rem);
  font-weight: 700;
  color: var(--text);
  line-height: 1.08;
  letter-spacing: -.01em;
  margin-bottom: 6px;
}
.hero-bio {
  color: var(--text-2);
  font-size: 1rem;
  line-height: 1.85;
  max-width: 440px;
  margin-bottom: 32px;
}
.hero-bio strong { color: var(--text); font-weight: 500; }
.hero-actions { display: flex; gap: 10px; flex-wrap: wrap; }
.btn {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-family: var(--font-mono);
  font-size: .74rem;
  letter-spacing: .04em;
  padding: 10px 20px;
  border-radius: var(--radius);
  border: 1px solid;
  transition: background .2s, color .2s, border-color .2s;
}
.btn-solid {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--bg);
  font-weight: 600;
}
.btn-solid:hover { background: transparent; color: var(--accent); text-decoration: none; }
.btn-outline {
  background: transparent;
  border-color: var(--border-hi);
  color: var(--text-2);
}
.btn-outline:hover { border-color: var(--accent); color: var(--accent); text-decoration: none; }

/* Terminal card (hero signature element) */
.terminal {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  font-family: var(--font-mono);
  font-size: .77rem;
  line-height: 1.9;
}
.term-bar {
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  padding: 9px 14px;
  display: flex;
  align-items: center;
  gap: 6px;
}
.dot { width: 10px; height: 10px; border-radius: 50%; }
.dr { background: #f05650; } .dy { background: #f5a623; } .dg { background: #27c93f; }
.term-file { font-size: .68rem; color: var(--text-3); margin: 0 auto; letter-spacing: .05em; }
.term-body { padding: 18px 16px; }
.tp { color: var(--accent); }
.tk { color: #7dd3fc; }
.tv { color: #86efac; }
.ts { color: #fdba74; }
.tm { color: var(--text-2); }
.tc {
  display: inline-block;
  width: 7px; height: 14px;
  background: var(--accent);
  margin-left: 1px;
  vertical-align: text-bottom;
  animation: blink .85s step-end infinite;
}
@keyframes blink { 50% { opacity: 0; } }

/* ============================================================
   ABOUT
============================================================ */
.about-grid {
  max-width: 700px;
}
.about-text p {
  color: var(--text-2);
  margin-bottom: 14px;
  font-size: 1rem;
  line-height: 1.9;
}
.about-text p:last-child { margin-bottom: 0; }
.about-text strong { color: var(--text); font-weight: 500; }
.about-edu {
  margin-top: 28px;
  padding-top: 22px;
  border-top: 1px solid var(--border);
}
.about-edu-title {
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 14px;
}
.edu-entry { margin-bottom: 14px; }
.edu-entry:last-child { margin-bottom: 0; }
.edu-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
}
.edu-school { font-size: .95rem; font-weight: 600; color: var(--text); }
.edu-period { font-family: var(--font-mono); font-size: .7rem; color: var(--info); white-space: nowrap; }
.edu-degree { font-size: .88rem; color: var(--text-2); margin-top: 3px; }

/* ============================================================
   SKILLS
============================================================ */
.skills-table { display: flex; flex-direction: column; }
.skill-row {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: 20px;
  padding: 16px 0;
  border-bottom: 1px solid var(--border);
  align-items: start;
}
.skill-cat {
  font-family: var(--font-mono);
  font-size: .68rem;
  color: #a8c5e0;
  letter-spacing: .1em;
  text-transform: uppercase;
  padding-top: 3px;
}
.tag-wrap { display: flex; flex-wrap: wrap; gap: 6px; }
.tag {
  font-family: var(--font-mono);
  font-size: .7rem;
  padding: 4px 10px;
  border: 1px solid var(--border-hi);
  border-radius: 4px;
  color: #dde8f4;
  background: var(--bg-card);
  transition: border-color .15s, color .15s;
  cursor: default;
}
.tag:hover { border-color: var(--accent); color: var(--accent); }

/* ============================================================
   EXPERIENCE
============================================================ */
.exp-entry { padding: 30px 0; border-bottom: 1px solid var(--border); }
.exp-entry:first-child { border-top: 1px solid var(--border); }
.exp-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 5px;
}
.exp-role { font-size: .98rem; font-weight: 600; color: var(--text); }
.exp-period {
  font-family: var(--font-mono);
  font-size: .7rem;
  color: var(--info);
}
.exp-org {
  font-family: var(--font-mono);
  font-size: .75rem;
  color: var(--accent);
  margin-bottom: 14px;
}
.exp-list { display: flex; flex-direction: column; gap: 7px; padding-left: 0; }
.exp-list li {
  font-size: .95rem;
  color: var(--text-2);
  line-height: 1.75;
  padding-left: 18px;
  position: relative;
}
.exp-list li::before {
  content: '\25B8';
  position: absolute;
  left: 0;
  color: var(--text-3);
  font-size: .7rem;
  top: 3px;
}
.exp-list li strong { color: var(--text); font-weight: 500; }

/* ============================================================
   PROJECTS
============================================================ */
.proj-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.proj-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 22px;
  display: flex;
  flex-direction: column;
  gap: 11px;
  transition: border-color .2s, transform .2s;
  position: relative;
  overflow: hidden;
}
.proj-card::after {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--accent), transparent);
  opacity: 0;
  transition: opacity .3s;
}
.proj-card:hover { border-color: var(--border-hi); transform: translateY(-1px); }
.proj-card:hover::after { opacity: 1; }
.proj-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 10px;
}
.proj-name { font-size: .93rem; font-weight: 600; color: var(--text); }
.proj-period {
  display: block;
  font-family: var(--font-mono);
  font-size: .64rem;
  color: var(--info);
  font-weight: 400;
  margin-top: 3px;
  letter-spacing: .03em;
}
.proj-link {
  font-family: var(--font-mono);
  font-size: .67rem;
  color: var(--accent);
  border: 1px solid var(--accent-dim);
  padding: 2px 8px;
  border-radius: 3px;
  white-space: nowrap;
  flex-shrink: 0;
  transition: background .15s;
}
.proj-link:hover { background: rgba(0, 212, 160, .08); text-decoration: none; }
.proj-desc { font-size: .92rem; color: var(--text-2); line-height: 1.75; flex: 1; }
.proj-desc strong { color: var(--text); font-weight: 600; }   /* replaces former inline styles */
.proj-tags { display: flex; flex-wrap: wrap; gap: 5px; margin-top: auto; }
.proj-tag {
  font-family: var(--font-mono);
  font-size: .66rem;
  padding: 2px 7px;
  border-radius: 3px;
  background: var(--bg-elevated);
  color: var(--text-3);
  border: 1px solid var(--border);
}

/* ============================================================
   RESEARCH
============================================================ */
.research-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
}
.research-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 22px;
  display: flex;
  flex-direction: column;
  gap: 11px;
  transition: border-color .2s, transform .2s;
  position: relative;
  overflow: hidden;
}
.research-card::after {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--accent), transparent);
  opacity: 0;
  transition: opacity .3s;
}
.research-card-wide { grid-column: 1 / -1; }
.research-card:hover { border-color: var(--border-hi); transform: translateY(-1px); }
.research-card:hover::after { opacity: 1; }
.research-head {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 10px;
}
.re-title { font-size: .93rem; font-weight: 600; color: var(--text); line-height: 1.4; }
.re-meta { font-family: var(--font-mono); font-size: .68rem; color: var(--info); letter-spacing: .01em; }
.re-badge {
  font-family: var(--font-mono);
  font-size: .67rem;
  padding: 3px 9px;
  border-radius: 3px;
  border: 1px solid;
  white-space: nowrap;
  flex-shrink: 0;
  transition: color .15s, border-color .15s;
}
.re-badge:hover { text-decoration: none; }
.badge-tlp  { color: var(--accent); border-color: var(--accent-dim); }
.badge-tlp:hover { background: rgba(0, 212, 160, .08); }
.badge-open { color: var(--accent); border-color: var(--accent-dim); }
.badge-open:hover { background: rgba(0, 212, 160, .08); }
.re-points { display: flex; flex-direction: column; gap: 6px; padding-top: 2px; }
.re-points li {
  font-size: .85rem;
  color: var(--text-2);
  line-height: 1.65;
  padding-left: 16px;
  position: relative;
}
.re-points li::before {
  content: '\25B8';
  position: absolute;
  left: 0;
  color: var(--text-3);
  font-size: .64rem;
  top: 4px;
}
.re-reference {
  margin-top: 4px;
  padding-top: 10px;
  border-top: 1px solid var(--border);
  font-family: var(--font-mono);
  font-size: .68rem;
  line-height: 1.7;
  color: var(--text-3);
}
.re-reference strong {
  color: var(--text-2);
  font-weight: 600;
  margin-right: 4px;
}
.re-reference em { color: var(--text-2); font-style: normal; }

/* ============================================================
   CONFERENCES
============================================================ */
.conf-entry {
  padding: 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
}
.conf-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 5px;
}
.conf-name { font-size: .98rem; font-weight: 600; color: var(--text); }
.conf-period {
  font-family: var(--font-mono);
  font-size: .7rem;
  color: var(--info);
  white-space: nowrap;
}
.conf-meta {
  font-family: var(--font-mono);
  font-size: .75rem;
  color: var(--accent);
  margin-bottom: 16px;
}
.conf-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  margin-bottom: 18px;
}
.conf-body p {
  color: var(--text-2);
  font-size: .93rem;
  line-height: 1.85;
  margin-bottom: 14px;
}
.conf-body p:last-child { margin-bottom: 0; }

/* ============================================================
   CERTIFICATIONS
============================================================ */
.certs-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 10px;
}

/* Filter pills */
.cert-filters {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 24px;
}
.cert-filter-btn {
  font-family: var(--font-mono);
  font-size: .72rem;
  letter-spacing: .03em;
  padding: 8px 18px;
  border-radius: 999px;
  border: 1px solid var(--border-hi);
  background: transparent;
  color: var(--text-2);
  transition: border-color .15s, color .15s, background .15s;
}
.cert-filter-btn:hover { border-color: var(--accent); color: var(--accent); }
.cert-filter-btn.active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--bg);
  font-weight: 600;
}
.cert-card.hidden { display: none; }
.cert-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 16px;
  transition: border-color .2s;
}
.cert-card:hover { border-color: var(--border-hi); }
.cert-name { font-size: .84rem; color: var(--text); line-height: 1.4; margin-bottom: 5px; }
.cert-link { color: var(--text); transition: color .15s; }
.cert-link:hover { color: var(--accent); text-decoration: none; }
.cert-issuer { font-family: var(--font-mono); font-size: .68rem; color: var(--info); }

/* ============================================================
   CONTACT
============================================================ */
.contact-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 56px;
  align-items: start;
}
.contact-bio { color: var(--text-2); font-size: 1rem; line-height: 1.9; margin-bottom: 20px; }
.contact-note {
  font-family: var(--font-mono);
  font-size: .7rem;
  color: var(--text-3);
  line-height: 1.7;
}
.contact-links { display: flex; flex-direction: column; gap: 9px; }
.contact-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 14px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: .84rem;
  color: var(--text-2);
  transition: border-color .2s, color .2s;
}
.contact-item:hover { border-color: var(--accent-dim); color: var(--text); text-decoration: none; }
.ci-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 1px solid var(--border-hi);
  flex-shrink: 0;
}
.ci-icon svg { width: 14px; height: 14px; fill: var(--accent); }
.ci-label {
  font-family: var(--font-mono);
  font-size: .65rem;
  color: var(--text-3);
  text-transform: uppercase;
  letter-spacing: .08em;
  display: block;
  margin-bottom: 1px;
}
.ci-value { font-size: .83rem; color: var(--text-2); }

/* ============================================================
   FOOTER
============================================================ */
footer {
  border-top: 1px solid var(--border);
  padding: 28px 0;
}
.footer-inner {
  display: flex;
  justify-content: center;
  align-items: center;
}
.footer-c {
  font-family: var(--font-mono);
  font-size: .68rem;
  color: var(--text-3);
}

/* ============================================================
   SCROLL ANIMATION
============================================================ */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity .55s ease, transform .55s ease;
}
.reveal.in { opacity: 1; transform: translateY(0); }

/* ============================================================
   RESPONSIVE
============================================================ */
/* Tablet */
@media (max-width: 900px) {
  .hero-layout { grid-template-columns: 1fr; gap: 40px; }
  .terminal { display: none; }
  .proj-grid { grid-template-columns: 1fr 1fr; gap: 12px; }
  .certs-grid { grid-template-columns: 1fr 1fr; }
  .contact-layout { grid-template-columns: 1fr; gap: 36px; }

  /* Nav collapses to a hamburger-triggered dropdown — 8 links no
     longer fit in a single row once "certifications" joined the list. */
  .nav-inner { justify-content: flex-end; position: relative; }
  .nav-toggle { display: flex; }
  .nav-links {
    position: fixed;
    top: 54px;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: rgba(8, 11, 15, .97);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid var(--border);
    max-height: 0;
    overflow: hidden;
    transition: max-height .3s ease;
  }
  .nav-links.open { max-height: calc(100vh - 54px); overflow-y: auto; }
  .nav-links a {
    display: block;
    padding: 16px 20px;
    font-size: .8rem;
    border-bottom: 1px solid var(--border);
  }
}

/* Large mobile */
@media (max-width: 768px) {
  section { padding: 64px 0 40px; }
  .wrap { padding: 0 16px; }
  .skill-row { grid-template-columns: 1fr; gap: 8px; }
  .proj-grid { grid-template-columns: 1fr; }
  .research-grid { grid-template-columns: 1fr; }
  .exp-head { flex-direction: column; gap: 4px; }
  .conf-head { flex-direction: column; gap: 4px; }
  .hero-name { font-size: clamp(1.8rem, 7vw, 2.5rem); }
  .sec-title { font-size: 1.35rem; }
}
/* Small mobile */
@media (max-width: 500px) {
  section { padding: 52px 0 32px; }
  .wrap { padding: 0 14px; }
  .certs-grid { grid-template-columns: 1fr; }
  .proj-grid { grid-template-columns: 1fr; }
  .hero-actions { flex-direction: column; }
  .hero-actions .btn { width: 100%; justify-content: center; }
  .contact-layout { gap: 28px; }
  .tag { font-size: .68rem; padding: 3px 8px; }
  .exp-list li { font-size: .9rem; }
}
/* Very small / older phones */
@media (max-width: 380px) {
  .wrap { padding: 0 12px; }
  .certs-grid { grid-template-columns: 1fr; }
  .hero-name { font-size: 1.7rem; }
}

/* ============================================================
   REDUCED MOTION — respect the OS preference
============================================================ */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
  }
  .reveal { opacity: 1; transform: none; }
  .tc { animation: none; }
}