/* ============================================================
   Tien M Nguyen — personal site
   Design concept: "Parse & Signal"
   His PhD centered on the grammatical-structure signatures that
   separate generated text from human text. The visual language
   borrows that idea: faint branching parse-tree linework as
   ambient texture, a warm "signal" amber used sparingly like a
   highlighter marking a detected match, set on an ink-teal ground.
   ============================================================ */

:root {
  /* ---- color tokens (light) ---- */
  --paper: #f2f4f1;
  --surface: #ffffff;
  --ink: #16232a;
  --ink-soft: #4b5d63;
  --line: #d8ded8;
  --signal: #a06a1f;
  --signal-ink: #1a1204;
  --signal-soft: #f0e0bd;
  --shadow: 0 1px 0 rgba(22, 35, 42, 0.06);

  /* ---- type tokens ---- */
  --font-display: "Iowan Old Style", "Palatino Linotype", Palatino, "URW Palladio L", Georgia, ui-serif, serif;
  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, "SFMono-Regular", "Cascadia Code", "Roboto Mono", Menlo, Consolas, monospace;

  --step-0: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  --step-1: clamp(1.15rem, 1.05rem + 0.5vw, 1.4rem);
  --step-2: clamp(1.5rem, 1.3rem + 1vw, 2rem);
  --step-3: clamp(2.1rem, 1.7rem + 2vw, 3.2rem);
  --step-4: clamp(2.8rem, 2.1rem + 3.5vw, 4.6rem);

  --content-w: 46rem;
  --wide-w: 62rem;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper: #0e1618;
    --surface: #141e21;
    --ink: #e7ece7;
    --ink-soft: #94a6a2;
    --line: #26363a;
    --signal: #e0aa4e;
    --signal-ink: #1a1204;
    --signal-soft: rgba(224, 170, 78, 0.14);
    --shadow: 0 1px 0 rgba(0, 0, 0, 0.4);
    color-scheme: dark;
  }
}

:root[data-theme="dark"] {
  --paper: #0e1618;
  --surface: #141e21;
  --ink: #e7ece7;
  --ink-soft: #94a6a2;
  --line: #26363a;
  --signal: #e0aa4e;
  --signal-ink: #1a1204;
  --signal-soft: rgba(224, 170, 78, 0.14);
  --shadow: 0 1px 0 rgba(0, 0, 0, 0.4);
  color-scheme: dark;
}

:root[data-theme="light"] {
  --paper: #f2f4f1;
  --surface: #ffffff;
  --ink: #16232a;
  --ink-soft: #4b5d63;
  --line: #d8ded8;
  --signal: #a06a1f;
  --signal-ink: #1a1204;
  --signal-soft: #f0e0bd;
  --shadow: 0 1px 0 rgba(22, 35, 42, 0.06);
  color-scheme: light;
}

* { box-sizing: border-box; }

html {
  scroll-padding-top: 5rem;
}

@media (prefers-reduced-motion: no-preference) {
  html { scroll-behavior: smooth; }
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--step-0);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

a {
  color: inherit;
  text-decoration-color: var(--line);
  text-underline-offset: 0.15em;
}
a:hover { text-decoration-color: var(--signal); }

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 3px;
}

h1, h2, h3 {
  font-family: var(--font-display);
  font-weight: 600;
  text-wrap: balance;
  margin: 0;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-soft);
}

.wrap {
  max-width: var(--content-w);
  margin-inline: auto;
  padding-inline: 1.5rem;
}
.wrap--wide {
  max-width: var(--wide-w);
}

/* ---- top nav ---- */
.nav {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.9rem 1.5rem;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}

.nav__mark {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  letter-spacing: 0.04em;
  color: var(--ink);
  text-decoration: none;
  white-space: nowrap;
}
.nav__mark b { color: var(--signal); font-weight: 600; }

.nav__links {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  list-style: none;
  margin: 0;
  padding: 0;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.nav__links a {
  text-decoration: none;
  color: var(--ink-soft);
  padding-bottom: 0.2rem;
  border-bottom: 1px solid transparent;
}
.nav__links a:hover,
.nav__links a.is-active {
  color: var(--ink);
  border-bottom-color: var(--signal);
}
.theme-toggle {
  border: 1px solid var(--line);
  background: var(--surface);
  color: var(--ink-soft);
  border-radius: 4px;
  width: 2rem;
  height: 2rem;
  display: grid;
  place-items: center;
  cursor: pointer;
  font-size: 0.9rem;
  line-height: 1;
  flex: none;
}
.theme-toggle:hover { color: var(--signal); border-color: var(--signal); }

@media (max-width: 640px) {
  .nav__links { gap: 0.85rem; font-size: 0.68rem; }
}

/* ---- hero ---- */
.hero {
  position: relative;
  padding: clamp(3rem, 6vw, 6rem) 1.5rem clamp(2.5rem, 5vw, 4rem);
  overflow: hidden;
}

.hero__canvas {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  opacity: 0.55;
}

.hero__inner {
  position: relative;
  z-index: 1;
  max-width: var(--wide-w);
  margin-inline: auto;
  display: grid;
  grid-template-columns: 1.35fr 0.65fr;
  gap: clamp(2rem, 5vw, 4rem);
  align-items: center;
}

@media (max-width: 760px) {
  .hero__inner { grid-template-columns: 1fr; }
  .hero__portrait { order: -1; width: 7.5rem; }
}

.hero__eyebrow {
  margin-bottom: 1rem;
}

.hero h1 {
  font-size: var(--step-4);
  line-height: 1.03;
  letter-spacing: -0.01em;
}

.hero__role {
  font-family: var(--font-mono);
  font-size: 0.95rem;
  color: var(--signal);
  margin-top: 0.9rem;
  letter-spacing: 0.02em;
}

.hero__lede {
  margin-top: 1.4rem;
  max-width: 38rem;
  color: var(--ink-soft);
  font-size: 1.08rem;
}

.hero__actions {
  margin-top: 2rem;
  display: flex;
  gap: 0.9rem;
  flex-wrap: wrap;
}

.btn {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  text-decoration: none;
  padding: 0.7rem 1.1rem;
  border-radius: 3px;
  border: 1px solid var(--line);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}
.btn--primary {
  background: var(--signal);
  border-color: var(--signal);
  color: var(--signal-ink);
  font-weight: 600;
}
.btn--primary:hover { filter: brightness(1.06); }
.btn--ghost {
  color: var(--ink);
  background: transparent;
}
.btn--ghost:hover { border-color: var(--signal); color: var(--signal); }

.hero__portrait {
  width: 100%;
  aspect-ratio: 1 / 1;
  border-radius: 6px;
  overflow: hidden;
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  justify-self: center;
  max-width: 15rem;
}
.hero__portrait img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* ---- sections ---- */
section {
  padding: clamp(3rem, 6vw, 4.5rem) 1.5rem;
  border-top: 1px solid var(--line);
}

.section__head {
  margin-bottom: 2.2rem;
}
.section__head h2 {
  font-size: var(--step-2);
  margin-top: 0.5rem;
}

/* ---- about ---- */
.about__body p {
  max-width: 40rem;
  color: var(--ink-soft);
  font-size: 1.05rem;
}
.about__body p + p { margin-top: 1rem; }

.about__meta {
  margin-top: 2rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));
  gap: 1.2rem 2rem;
  max-width: var(--wide-w);
}
.about__meta dt {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-soft);
}
.about__meta dd {
  margin: 0.3rem 0 0;
  font-size: 0.95rem;
}

/* ---- experience timeline ---- */
.timeline {
  max-width: var(--wide-w);
  position: relative;
}
.timeline::before {
  content: "";
  position: absolute;
  left: 8.4rem;
  top: 0.5rem;
  bottom: 0.5rem;
  width: 1px;
  background: var(--line);
}
@media (max-width: 640px) {
  .timeline::before { left: 0.4rem; }
}

.tl-item {
  position: relative;
  display: grid;
  grid-template-columns: 8.4rem 1fr;
  gap: 1.5rem;
  padding: 1.3rem 0;
}
.tl-item + .tl-item { border-top: 1px dashed var(--line); }

@media (max-width: 640px) {
  .tl-item { grid-template-columns: 1fr; padding-left: 1.2rem; gap: 0.4rem; }
}

.tl-item::after {
  content: "";
  position: absolute;
  left: 8.4rem;
  top: 1.7rem;
  width: 9px;
  height: 9px;
  margin-left: -4.5px;
  border-radius: 50%;
  background: var(--paper);
  border: 2px solid var(--signal);
}
@media (max-width: 640px) {
  .tl-item::after { left: 0.4rem; }
}

.tl-date {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--ink-soft);
  padding-top: 0.2rem;
  font-variant-numeric: tabular-nums;
}

.tl-role {
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-weight: 600;
}

.tl-org {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--signal);
  margin-top: 0.15rem;
}

.tl-desc {
  margin-top: 0.6rem;
  color: var(--ink-soft);
  max-width: 40rem;
}
.tl-desc strong { color: var(--ink); font-weight: 600; }

/* ---- education ---- */
.edu-grid {
  display: grid;
  gap: 1.4rem;
  max-width: var(--wide-w);
}
.edu-item {
  display: grid;
  grid-template-columns: 8.4rem 1fr;
  gap: 1.5rem;
}
@media (max-width: 640px) {
  .edu-item { grid-template-columns: 1fr; gap: 0.3rem; }
}
.edu-date {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--ink-soft);
  font-variant-numeric: tabular-nums;
}
.edu-title { font-weight: 600; }
.edu-org { color: var(--ink-soft); font-size: 0.92rem; margin-top: 0.15rem; }
.edu-detail { font-style: italic; color: var(--ink-soft); margin-top: 0.3rem; font-size: 0.92rem; }

/* ---- projects ---- */
.project-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(17rem, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  max-width: var(--wide-w);
}
.project-card {
  background: var(--surface);
  padding: 1.4rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
.project-card__head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 0.5rem;
}
.project-card h3 {
  font-size: 1.02rem;
  line-height: 1.3;
}
.project-card__year {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--ink-soft);
  white-space: nowrap;
  font-variant-numeric: tabular-nums;
}
.project-card__org {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--signal);
}
.project-card p {
  color: var(--ink-soft);
  font-size: 0.92rem;
  margin: 0;
}
.tags {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  padding: 0;
  margin: 0.2rem 0 0;
}
.tags li {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.02em;
  padding: 0.2rem 0.5rem;
  background: var(--signal-soft);
  color: var(--ink);
  border-radius: 3px;
}

/* ---- publications ---- */
.pub-list {
  list-style: none;
  margin: 0;
  padding: 0;
  max-width: var(--wide-w);
  display: grid;
  gap: 1.1rem;
}
.pub-list li {
  display: grid;
  grid-template-columns: 10rem 1fr;
  gap: 1.5rem;
  padding-bottom: 1.1rem;
  border-bottom: 1px solid var(--line);
}
@media (max-width: 640px) {
  .pub-list li { grid-template-columns: 1fr; gap: 0.25rem; }
}
.pub-venue {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  color: var(--ink-soft);
}
.pub-title {
  font-family: var(--font-display);
  font-style: italic;
  font-size: 1rem;
}

/* ---- skills / languages ---- */
.skills-langs {
  display: grid;
  grid-template-columns: 1.3fr 1fr;
  gap: 3rem;
  max-width: var(--wide-w);
}
@media (max-width: 640px) {
  .skills-langs { grid-template-columns: 1fr; gap: 2rem; }
}
.pill-row {
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  padding: 0;
  margin: 0;
}
.pill-row li {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  padding: 0.4rem 0.7rem;
  border: 1px solid var(--line);
  border-radius: 3px;
  color: var(--ink);
}
.lang-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: grid;
  gap: 0.55rem;
}
.lang-list li {
  display: flex;
  justify-content: space-between;
  font-size: 0.92rem;
  border-bottom: 1px dashed var(--line);
  padding-bottom: 0.55rem;
}
.lang-list b { font-weight: 600; }
.lang-list span { color: var(--ink-soft); font-family: var(--font-mono); font-size: 0.78rem; }

/* ---- contact ---- */
.contact {
  text-align: left;
}
.contact__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr));
  gap: 1.4rem;
  max-width: var(--wide-w);
  margin-top: 2rem;
}
.contact__card {
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1.1rem 1.2rem;
  background: var(--surface);
  text-decoration: none;
  display: block;
}
.contact__card:hover { border-color: var(--signal); }
.contact__card .eyebrow { margin-bottom: 0.4rem; }
.contact__card strong {
  font-family: var(--font-mono);
  font-size: 0.92rem;
  word-break: break-word;
}

footer {
  padding: 2rem 1.5rem 3rem;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--ink-soft);
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}
footer a { text-decoration: none; }
footer a:hover { color: var(--signal); }