/* ============================================================
   Field Notes — engineering-notebook aesthetic
   Palette:
     paper      #FDFDFB
     grid line  #E3ECF4  (faint quad-rule blue)
     ink        #22303C
     margin red #D9472B  (the notebook margin rule — signature)
     ballpoint  #2B59A8  (links, actions)
     highlight  #FFE45E  (marker highlights)
   Type:
     display  Zilla Slab   (textbook slab serif)
     body     Karla
     utility  IBM Plex Mono
   ============================================================ */

:root {
  --paper: #fdfdfb;
  --grid: #e3ecf4;
  --ink: #22303c;
  --ink-soft: #5b6b7a;
  --margin-red: #d9472b;
  --ballpoint: #2b59a8;
  --highlight: #ffe45e;
  --card: #ffffff;
  --rule: #cdd9e4;

  --font-display: "Zilla Slab", Georgia, serif;
  --font-body: "Karla", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, monospace;

  --margin-x: 84px; /* width of the red-margin gutter on desktop */
  --content-max: 880px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  color: var(--ink);
  line-height: 1.65;
  font-size: 1.0625rem;
  /* quad-rule graph paper */
  background-color: var(--paper);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 28px 28px;
}

/* ---------- the red margin rule (signature) ---------- */
.margin-rule {
  position: fixed;
  top: 0;
  bottom: 0;
  left: var(--margin-x);
  width: 2px;
  background: var(--margin-red);
  opacity: 0.85;
  z-index: 1;
  pointer-events: none;
}

/* ---------- utilities ---------- */
.mono { font-family: var(--font-mono); }

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--ink);
  color: var(--paper);
  padding: 0.5rem 1rem;
  z-index: 10;
}
.skip-link:focus { left: 0; }

a { color: var(--ballpoint); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--margin-red); }
a:focus-visible,
button:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--ballpoint);
  outline-offset: 2px;
}

/* ---------- header ---------- */
.site-header {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  padding: 1.25rem 2rem 1.25rem calc(var(--margin-x) + 28px);
  border-bottom: 1px solid var(--rule);
  background: rgba(253, 253, 251, 0.92);
  backdrop-filter: blur(3px);
  position: sticky;
  top: 0;
  z-index: 5;
}

.site-mark {
  font-size: 0.8rem;
  letter-spacing: 0.18em;
  color: var(--margin-red);
  font-weight: 500;
  text-decoration: none;
}
.site-mark:hover { color: var(--ink); }

.site-nav { display: flex; gap: 1.4rem; flex-wrap: wrap; }
.site-nav a {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--ink);
  text-decoration: none;
  padding-bottom: 2px;
}
.site-nav a:hover { color: var(--margin-red); }
.site-nav a[aria-current="page"] {
  color: var(--margin-red);
  border-bottom: 2px solid var(--margin-red);
}

/* ---------- layout ---------- */
main { padding-left: calc(var(--margin-x) + 28px); padding-right: 2rem; }
.hero, .section { max-width: var(--content-max); }

/* ---------- hero ---------- */
.hero { padding: 4.5rem 0 3rem; }

.eyebrow {
  font-size: 0.8rem;
  letter-spacing: 0.14em;
  color: var(--ink-soft);
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

h1 {
  font-family: var(--font-display);
  font-weight: 700;
  font-size: clamp(2.6rem, 6vw, 4.2rem);
  line-height: 1.05;
  letter-spacing: -0.01em;
}

.tagline {
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 1.35rem;
  color: var(--ink-soft);
  margin-top: 0.5rem;
}

.intro { margin-top: 1.5rem; max-width: 60ch; }

.hero-links { margin-top: 1.75rem; display: flex; gap: 0.75rem; flex-wrap: wrap; }
.hero-links a {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  text-decoration: none;
  border: 1px solid var(--ink);
  color: var(--ink);
  padding: 0.4rem 0.9rem;
  background: var(--card);
  transition: transform 120ms ease, box-shadow 120ms ease;
}
.hero-links a:hover {
  color: var(--margin-red);
  border-color: var(--margin-red);
  transform: translate(-1px, -1px);
  box-shadow: 2px 2px 0 var(--margin-red);
}

/* ---------- sections ---------- */
.section { position: relative; padding: 3.5rem 0; border-top: 1px dashed var(--rule); }

/* rotated label sitting in the red margin gutter */
.section-label {
  position: absolute;
  left: calc(-1 * (var(--margin-x) + 28px) + 14px);
  top: 4rem;
  transform: rotate(180deg);
  writing-mode: vertical-rl;
  font-size: 0.72rem;
  letter-spacing: 0.22em;
  color: var(--margin-red);
  white-space: nowrap;
}

h2 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(1.8rem, 3.5vw, 2.4rem);
  display: inline;
  /* highlighter swipe */
  background: linear-gradient(transparent 58%, var(--highlight) 58%, var(--highlight) 92%, transparent 92%);
  padding: 0 0.15em;
}

.section-lede { margin-top: 1rem; color: var(--ink-soft); max-width: 55ch; }

/* ---------- filters ---------- */
.filter-row { margin-top: 1.75rem; display: flex; gap: 0.5rem; flex-wrap: wrap; }
.filter-btn {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  border: 1px solid var(--rule);
  background: var(--card);
  color: var(--ink-soft);
  padding: 0.3rem 0.8rem;
  cursor: pointer;
}
.filter-btn[aria-pressed="true"] {
  border-color: var(--ink);
  color: var(--ink);
  background: var(--highlight);
}

/* ---------- cards ---------- */
.card-grid {
  margin-top: 1.5rem;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.25rem;
}

.card {
  background: var(--card);
  border: 1px solid var(--rule);
  padding: 1.4rem 1.4rem 1.2rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
  position: relative;
  transition: transform 140ms ease, box-shadow 140ms ease;
  color: var(--ink);
  text-decoration: none;
}
.card:hover {
  transform: translate(-2px, -2px);
  box-shadow: 4px 4px 0 var(--grid), 5px 5px 0 var(--rule);
  color: var(--ink);
  border-color: var(--ink);
}

.card-more {
  font-size: 0.78rem;
  color: var(--ballpoint);
  letter-spacing: 0.06em;
}
.card:hover .card-more { color: var(--margin-red); }

/* section heading row on the home page: title + link to the full page */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}
.section-page-link {
  font-size: 0.78rem;
  letter-spacing: 0.1em;
  text-decoration: none;
  color: var(--ballpoint);
  white-space: nowrap;
}
.section-page-link:hover { color: var(--margin-red); text-decoration: underline; }

.card h3 {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.25rem;
  line-height: 1.25;
}

.card .card-date {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--ink-soft);
  letter-spacing: 0.08em;
}

.card p { font-size: 0.97rem; }

.tag-row { display: flex; gap: 0.4rem; flex-wrap: wrap; margin-top: auto; padding-top: 0.5rem; }
.tag {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  color: var(--ballpoint);
  border: 1px solid currentColor;
  padding: 0.1rem 0.5rem;
  border-radius: 999px;
}

.card-link { font-weight: 700; font-size: 0.95rem; }

/* ---------- research list ---------- */
.research-list { margin-top: 1.75rem; list-style: none; counter-reset: paper; }
.research-item {
  counter-increment: paper;
  border-left: 3px solid var(--ballpoint);
  background: var(--card);
  border-top: 1px solid var(--rule);
  border-right: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  padding: 1.2rem 1.4rem;
  margin-bottom: 1rem;
}
.research-item h3 {
  font-family: var(--font-display);
  font-size: 1.2rem;
  font-weight: 600;
}
.research-item h3::before {
  content: "[" counter(paper) "] ";
  font-family: var(--font-mono);
  font-size: 0.85rem;
  color: var(--margin-red);
}
.research-venue {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--ink-soft);
  margin-top: 0.2rem;
}
.research-item p { margin-top: 0.5rem; font-size: 0.97rem; }
.research-item a { font-weight: 700; font-size: 0.95rem; }

/* ---------- coursework ---------- */
.term-block { margin-top: 1.75rem; }
.term-title {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--margin-red);
  border-bottom: 1px solid var(--rule);
  padding-bottom: 0.4rem;
}
.course-list { list-style: none; margin-top: 0.6rem; }
.course-list li {
  display: flex;
  gap: 0.75rem;
  align-items: baseline;
  padding: 0.5rem 0;
  border-bottom: 1px dotted var(--rule);
  flex-wrap: wrap;
}
.course-name { font-weight: 700; }
.course-note { color: var(--ink-soft); font-size: 0.95rem; }
.course-list a { font-size: 0.9rem; }

/* ---------- contact form ---------- */
#contact-form { margin-top: 1.75rem; max-width: 540px; }
.form-row { margin-bottom: 1.1rem; display: flex; flex-direction: column; gap: 0.35rem; }
.form-row label {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-soft);
}
input, textarea {
  font-family: var(--font-body);
  font-size: 1rem;
  color: var(--ink);
  background: var(--card);
  border: 1px solid var(--rule);
  padding: 0.65rem 0.8rem;
  width: 100%;
  resize: vertical;
}
input:focus, textarea:focus { border-color: var(--ballpoint); }

.btn {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  background: var(--ink);
  color: var(--paper);
  border: 1px solid var(--ink);
  padding: 0.65rem 1.5rem;
  cursor: pointer;
  transition: transform 120ms ease, box-shadow 120ms ease;
}
.btn:hover { transform: translate(-1px, -1px); box-shadow: 3px 3px 0 var(--margin-red); }
.btn:disabled { opacity: 0.6; cursor: wait; transform: none; box-shadow: none; }

.form-status { margin-top: 0.9rem; font-size: 0.85rem; min-height: 1.2em; }
.form-status.ok { color: #1d7a3f; }
.form-status.err { color: var(--margin-red); }

/* ---------- standalone pages ---------- */
.page-section { border-top: none; padding-top: 3.5rem; }

.page-title {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: clamp(2rem, 4.5vw, 3rem);
  line-height: 1.1;
  display: inline;
  background: linear-gradient(transparent 58%, var(--highlight) 58%, var(--highlight) 92%, transparent 92%);
  padding: 0 0.15em;
}

.quiet-link { color: var(--ink); text-decoration: none; }
.quiet-link:hover { color: var(--margin-red); text-decoration: underline; }

/* ---------- detail pages ---------- */
.detail-page { max-width: 720px; }

.back-link {
  text-decoration: none;
  color: var(--margin-red);
  letter-spacing: 0.1em;
}
.back-link:hover { text-decoration: underline; }

.detail-page h1 {
  font-size: clamp(2rem, 5vw, 3.2rem);
  margin-top: 0.5rem;
}

.detail-meta {
  font-size: 0.8rem;
  color: var(--ink-soft);
  letter-spacing: 0.08em;
  margin-top: 0.75rem;
}

.detail-tags { margin-top: 0.9rem; padding-top: 0; }

.detail-lede {
  margin-top: 1.5rem;
  font-family: var(--font-display);
  font-weight: 500;
  font-size: 1.25rem;
  color: var(--ink-soft);
  line-height: 1.5;
}

.detail-body { margin-top: 1.75rem; }
.detail-body p { margin-bottom: 1.1rem; max-width: 65ch; }

.detail-h {
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 1.45rem;
  margin: 2rem 0 0.75rem;
  background: none;
  padding: 0;
  display: block;
}
.detail-h::before {
  content: "§ ";
  color: var(--margin-red);
}

.detail-list { margin: 0 0 1.1rem 1.25rem; max-width: 62ch; }
.detail-list li { margin-bottom: 0.4rem; }
.detail-list li::marker { color: var(--margin-red); }

.detail-quote {
  border-left: 3px solid var(--highlight);
  background: var(--card);
  border-top: 1px solid var(--rule);
  border-right: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  padding: 1rem 1.25rem;
  margin: 1.5rem 0;
  font-family: var(--font-display);
  font-size: 1.15rem;
  font-style: italic;
}

.detail-figure { margin: 1.75rem 0; }
.detail-figure img {
  width: 100%;
  height: auto;
  display: block;
  border: 1px solid var(--rule);
  background: var(--card);
  padding: 6px; /* photo-corner feel */
}
.detail-figure figcaption {
  font-size: 0.75rem;
  color: var(--ink-soft);
  margin-top: 0.5rem;
  letter-spacing: 0.05em;
}

.detail-links { margin-top: 2rem; }

/* ---------- footer ---------- */
.site-footer {
  margin-top: 2rem;
  padding: 2rem 2rem 2.5rem calc(var(--margin-x) + 28px);
  border-top: 1px solid var(--rule);
  color: var(--ink-soft);
  font-size: 0.8rem;
}

/* ---------- responsive ---------- */
@media (max-width: 720px) {
  :root { --margin-x: 26px; }
  .site-header { padding-left: calc(var(--margin-x) + 16px); padding-right: 1.25rem; }
  main { padding-left: calc(var(--margin-x) + 16px); padding-right: 1.25rem; }
  .site-footer { padding-left: calc(var(--margin-x) + 16px); }
  .section-label { display: none; }
  body { background-size: 24px 24px; }
}

/* ---------- reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .card, .btn, .hero-links a { transition: none; }
  .card:hover, .btn:hover, .hero-links a:hover { transform: none; }
}