/* ==========================================================================
   Derek Han — Engineering Portfolio
   Design direction: Technical / Engineering
   ========================================================================== */

/* ---------- Theme tokens ---------- */
:root {
  --bg: #eef0f2;
  --bg-elev: #ffffff;
  --bg-sunken: #e4e7ea;
  --ink: #1a1d21;
  --muted: #5a6472;
  --line: #d3d8de;
  --line-strong: #b9c1ca;
  --accent: #2b6cb0;
  --accent-soft: rgba(43, 108, 176, 0.12);
  --accent-2: #e8590c;
  --accent-2-soft: rgba(232, 89, 12, 0.12);
  --shadow: 0 1px 2px rgba(16, 20, 26, 0.06), 0 8px 24px rgba(16, 20, 26, 0.05);
  --hero-tint: rgba(238, 240, 242, 0.68);

  --font-sans: "IBM Plex Sans", system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --wrap: 1100px;
  --radius: 6px;
  --header-h: 64px;
}

[data-theme="dark"] {
  --bg: #0f1115;
  --bg-elev: #161a20;
  --bg-sunken: #0b0d10;
  --ink: #e6e8eb;
  --muted: #9aa4b2;
  --line: #262c34;
  --line-strong: #333b45;
  --accent: #5aa2e0;
  --accent-soft: rgba(90, 162, 224, 0.16);
  --accent-2: #ff7a3d;
  --accent-2-soft: rgba(255, 122, 61, 0.16);
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 12px 28px rgba(0, 0, 0, 0.35);
  --hero-tint: rgba(15, 17, 21, 0.8);
}

/* ---------- Reset ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3, h4 { line-height: 1.2; margin: 0 0 0.5em; font-weight: 600; letter-spacing: -0.01em; }
p { margin: 0 0 1em; }

code, kbd, samp { font-family: var(--font-mono); }

::selection { background: var(--accent-soft); }

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

.skip-link {
  position: absolute;
  left: -999px;
  top: 0;
  background: var(--accent);
  color: #fff;
  padding: 8px 14px;
  z-index: 200;
}
.skip-link:focus { left: 8px; top: 8px; }

/* ---------- Layout ---------- */
.wrap {
  width: 100%;
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: 24px;
}

main { display: block; }

section { padding-block: 64px; }

.section-head { margin-bottom: 32px; }

.kicker {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-2);
  display: block;
  margin-bottom: 8px;
}

.section-head h2 { font-size: clamp(1.6rem, 3vw, 2.1rem); margin: 0; }

.rule {
  height: 1px;
  background: var(--line);
  border: 0;
  margin: 24px 0;
}

.lead { font-size: 1.15rem; color: var(--muted); max-width: 62ch; }
.muted { color: var(--muted); }

/* ---------- Header / nav ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg);
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: 16px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  color: var(--ink);
  font-weight: 600;
  margin-right: auto;
}
.brand:hover { text-decoration: none; }

.brand-mark {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  border-radius: 5px;
  letter-spacing: 0.02em;
}

.site-nav { display: flex; align-items: center; gap: 4px; }

.site-nav a {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  color: var(--muted);
  padding: 8px 10px;
  border-radius: 4px;
  white-space: nowrap;
}
.site-nav a:hover { color: var(--ink); background: var(--bg-sunken); text-decoration: none; }
.site-nav a[aria-current="page"] { color: var(--accent); background: var(--accent-soft); }

.theme-toggle,
.nav-toggle {
  background: transparent;
  border: 1px solid var(--line);
  color: var(--ink);
  width: 40px;
  height: 40px;
  border-radius: 5px;
  cursor: pointer;
  display: grid;
  place-items: center;
  flex: none;
}
.theme-toggle:hover, .nav-toggle:hover { border-color: var(--line-strong); }

.nav-toggle { display: none; }
.theme-toggle svg { width: 18px; height: 18px; }
.theme-toggle .icon-moon { display: none; }
[data-theme="dark"] .theme-toggle .icon-sun { display: none; }
[data-theme="dark"] .theme-toggle .icon-moon { display: block; }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  border-bottom: 1px solid var(--line);
  background: var(--bg);
  overflow: hidden;
}
.hero-banner {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  object-fit: cover;
  object-position: center;
  z-index: 0;
}
/* Blueprint grid, kept crisp on top of a tinted banner */
.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px),
    linear-gradient(var(--hero-tint), var(--hero-tint));
  background-size: 48px 48px, 48px 48px, auto;
  background-position: center, center, center;
}
.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 2;
  background: linear-gradient(180deg, transparent 40%, var(--bg) 100%);
  pointer-events: none;
}
.hero .wrap { position: relative; z-index: 3; }
.hero-inner { padding-block: 88px 72px; }

.hero-grid {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 48px;
  align-items: center;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 16px;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.eyebrow::before { content: ""; width: 28px; height: 1px; background: var(--accent); }

.hero h1 {
  font-size: clamp(2.2rem, 5.5vw, 3.6rem);
  margin: 0 0 16px;
}
.hero .lead { font-size: 1.2rem; }

.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; }

.avatar {
  width: 210px;
  height: 210px;
  border-radius: 8px;
  object-fit: cover;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  box-shadow: var(--shadow);
}

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  padding: 11px 18px;
  border-radius: 5px;
  border: 1px solid var(--line-strong);
  background: var(--bg-elev);
  color: var(--ink);
  cursor: pointer;
  transition: transform 0.12s ease, border-color 0.12s ease, background 0.12s ease;
}
.btn:hover { text-decoration: none; border-color: var(--accent); transform: translateY(-1px); }
.btn--primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn--primary:hover { color: #fff; }
.btn--ghost { background: transparent; }

/* ---------- Cards & grids ---------- */
.grid { display: grid; gap: 22px; }
.grid--2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid--3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }

.card {
  background: var(--bg-elev);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
  display: flex;
  flex-direction: column;
}
.card:hover { transform: translateY(-3px); box-shadow: var(--shadow); border-color: var(--line-strong); }

.card-media {
  aspect-ratio: 16 / 10;
  background: var(--bg-sunken);
  border-bottom: 1px solid var(--line);
  overflow: hidden;
}
.card-media img { width: 100%; height: 100%; object-fit: cover; }

.card-body { padding: 18px 20px 22px; display: flex; flex-direction: column; flex: 1; }

.card-meta {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.04em;
  color: var(--muted);
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
  margin-bottom: 10px;
}
.card-meta .dot { color: var(--line-strong); }

.card-title { font-size: 1.15rem; margin: 0 0 8px; }
.card-title a { color: var(--ink); }
.card-title a:hover { color: var(--accent); text-decoration: none; }

.card p { color: var(--muted); font-size: 0.95rem; margin: 0 0 14px; }
.card .card-foot { margin-top: auto; }

/* ---------- Tags ---------- */
.tags { display: flex; flex-wrap: wrap; gap: 6px; }
.tag {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  padding: 3px 8px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  border: 1px solid transparent;
  white-space: nowrap;
}
.tag--accent2 { background: var(--accent-2-soft); color: var(--accent-2); }

/* ---------- Filter bar ---------- */
.filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 28px;
}
.filter-btn {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  padding: 7px 13px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--bg-elev);
  color: var(--muted);
  cursor: pointer;
}
.filter-btn:hover { border-color: var(--line-strong); color: var(--ink); }
.filter-btn[aria-pressed="true"] {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}


.empty-state {
  border: 1px dashed var(--line-strong);
  border-radius: var(--radius);
  padding: 40px 24px;
  text-align: center;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  background: var(--bg-elev);
}

/* Links whose bound href was empty (e.g. a plain-text contact row) */
.no-link {
  color: var(--muted) !important;
  text-decoration: none;
  pointer-events: none;
}

/* Shown when content JSON cannot be loaded (e.g. opened without a server) */
.content-error {
  max-width: var(--wrap);
  margin: 24px auto;
  padding: 16px 20px;
  border: 1px solid var(--accent-2);
  background: var(--accent-2-soft);
  border-radius: var(--radius);
  font-size: 0.9rem;
}
.content-error code {
  background: var(--bg-sunken);
  padding: 1px 5px;
  border-radius: 3px;
}

/* ---------- Timeline (experience) ---------- */
.timeline { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--line); }
.timeline > li { position: relative; padding: 0 0 36px 28px; }
.timeline > li::before {
  content: "";
  position: absolute;
  left: -5px;
  top: 8px;
  width: 9px;
  height: 9px;
  border-radius: 50%;
  background: var(--accent);
  border: 2px solid var(--bg);
}
.timeline h3 { margin: 0 0 4px; font-size: 1.15rem; }

.entry-head {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 8px;
}
.entry-head .when { font-family: var(--font-mono); font-size: 0.78rem; color: var(--muted); }

.bullets { margin: 10px 0 0; padding-left: 18px; color: var(--muted); }
.bullets li { margin-bottom: 4px; }

/* ---------- Skills ---------- */
.skill-group { margin-bottom: 26px; }
.skill-group h3 {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 12px;
}
.skill-list { display: flex; flex-wrap: wrap; gap: 8px; }
.chip {
  font-family: var(--font-mono);
  font-size: 0.82rem;
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 4px;
  background: var(--bg-elev);
}

/* ---------- Resume ---------- */
.resume-head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.resume-contact { font-family: var(--font-mono); font-size: 0.85rem; color: var(--muted); }
.resume-contact a { color: var(--accent); }
.resume-section { padding-block: 28px; border-top: 1px solid var(--line); }

/* ---------- Prose / article ---------- */
.prose { max-width: 72ch; }
.prose h2 { margin-top: 1.4em; font-size: 1.4rem; }
.prose h3 { margin-top: 1.2em; font-size: 1.15rem; }
.prose ul { padding-left: 20px; }
.prose img { border-radius: var(--radius); border: 1px solid var(--line); margin: 1em 0; }
.prose code {
  background: var(--bg-sunken);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  font-size: 0.88em;
}

/* ---------- Contact ---------- */
.contact-list { list-style: none; padding: 0; margin: 0; }
.contact-list li {
  display: flex;
  gap: 16px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line);
}
.contact-list .label {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
  min-width: 120px;
  padding-top: 4px;
}

/* ---------- Blog ---------- */
.post-list { list-style: none; padding: 0; margin: 0; }
.post-list li { padding: 20px 0; border-bottom: 1px solid var(--line); }
.post-list h3 { margin: 0 0 4px; }
.post-list time { font-family: var(--font-mono); font-size: 0.76rem; color: var(--muted); }

/* ---------- Page header ---------- */
.page-head {
  border-bottom: 1px solid var(--line);
  padding-block: 56px 40px;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 48px 48px;
}
.page-head h1 { font-size: clamp(1.9rem, 4vw, 2.8rem); margin: 0 0 10px; }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--line);
  padding-block: 40px;
  margin-top: 40px;
  background: var(--bg-sunken);
}
.footer-inner {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--muted);
}
.footer-links { display: flex; flex-wrap: wrap; gap: 16px; }
.footer-links a { color: var(--muted); }
.footer-links a:hover { color: var(--accent); }

/* ---------- Scroll reveal ---------- */
.reveal { opacity: 0; transform: translateY(16px); transition: opacity 0.5s ease, transform 0.5s ease; }
.reveal.is-visible { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
  .card, .btn { transition: none; }
}

/* ---------- Responsive ---------- */
@media (max-width: 860px) {
  .hero-grid { grid-template-columns: 1fr; }
  .avatar { width: 150px; height: 150px; order: -1; }
  .grid--3 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}

@media (max-width: 720px) {
  .nav-toggle { display: grid; }
  .site-nav {
    position: absolute;
    top: var(--header-h);
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    background: var(--bg-elev);
    border-bottom: 1px solid var(--line);
    padding: 8px;
    display: none;
  }
  .site-nav.is-open { display: flex; }
  .site-nav a { padding: 12px 14px; font-size: 0.9rem; }

  .grid--3, .grid--2 { grid-template-columns: 1fr; }
  section { padding-block: 48px; }
  .hero-inner { padding-block: 64px 52px; }
  .contact-list li { flex-direction: column; gap: 4px; }
  .contact-list .label { min-width: 0; }
}

/* ---------- Project image gallery (horizontal slider) ---------- */
.project-gallery-wrap {
  position: relative;
  margin: 0 0 26px;
}
.project-gallery {
  display: flex;
  gap: 14px;
  overflow-x: auto;
  scroll-snap-type: x mandatory;
  scroll-behavior: smooth;
  padding-bottom: 10px;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
  scrollbar-color: var(--line-strong) transparent;
}
.project-gallery::-webkit-scrollbar { height: 8px; }
.project-gallery::-webkit-scrollbar-track { background: transparent; }
.project-gallery::-webkit-scrollbar-thumb { background: var(--line-strong); border-radius: 999px; }

.project-figure {
  flex: 0 0 auto;
  width: min(420px, 78%);
  margin: 0;
  scroll-snap-align: start;
}
.project-figure img {
  width: 100%;
  margin: 0;
  aspect-ratio: 4 / 3;
  object-fit: cover;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  cursor: zoom-in;
  transition: transform 0.15s ease, border-color 0.15s ease;
}
.project-figure img:hover { transform: translateY(-2px); border-color: var(--line-strong); }
.project-figure figcaption {
  font-family: var(--font-mono);
  font-size: 0.76rem;
  color: var(--muted);
  margin-top: 8px;
  text-align: center;
}

/* One image: no slider, just full width */
.project-gallery--single { display: block; overflow: visible; }
.project-gallery--single .project-figure { width: 100%; }
.project-gallery--single .project-figure img {
  aspect-ratio: auto;
  max-height: 520px;
  object-fit: contain;
  background: var(--bg-sunken);
}

/* Slider arrows */
.project-gallery-nav {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 40px;
  height: 40px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--bg-elev);
  color: var(--ink);
  font-size: 1.3rem;
  line-height: 1;
  cursor: pointer;
  box-shadow: var(--shadow);
  z-index: 2;
}
.project-gallery-nav:hover { border-color: var(--line-strong); }
.project-gallery-nav[hidden] { display: none; }
.gallery-prev { left: -6px; }
.gallery-next { right: -6px; }

@media (max-width: 720px) {
  .project-figure { width: 82%; }
  .gallery-prev { left: 2px; }
  .gallery-next { right: 2px; }
}

/* ---------- Gallery ---------- */
.gallery-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;
}
.gallery-item {
  position: relative;
  display: block;
  padding: 0;
  aspect-ratio: 1 / 1;
  overflow: hidden;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--bg-elev);
  cursor: zoom-in;
}
.gallery-item img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.3s ease;
}
.gallery-item:hover img,
.gallery-item:focus-visible img { transform: scale(1.05); }
.gallery-cap {
  position: absolute;
  left: 0;
  right: 0;
  bottom: 0;
  padding: 6px 8px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  color: #fff;
  text-align: left;
  background: linear-gradient(transparent, rgba(0, 0, 0, 0.65));
  opacity: 0;
  transition: opacity 0.2s ease;
}
.gallery-item:hover .gallery-cap,
.gallery-item:focus-visible .gallery-cap { opacity: 1; }

/* ---------- Lightbox ---------- */
body.lightbox-open { overflow: hidden; }

.lightbox {
  position: fixed;
  inset: 0;
  z-index: 300;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
  background: rgba(10, 12, 15, 0.92);
}
.lightbox[hidden] { display: none; }

.lightbox-fig {
  margin: 0;
  max-width: min(1100px, 92vw);
  max-height: 88vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
}
.lightbox-fig img {
  max-width: 100%;
  max-height: 80vh;
  border-radius: 6px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
}
.lightbox-cap {
  color: #e6e8eb;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  text-align: center;
}

.lightbox-close,
.lightbox-prev,
.lightbox-next {
  position: absolute;
  display: grid;
  place-items: center;
  width: 44px;
  height: 44px;
  border: 1px solid rgba(255, 255, 255, 0.25);
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.08);
  color: #fff;
  font-size: 1.4rem;
  line-height: 1;
  cursor: pointer;
}
.lightbox-close:hover,
.lightbox-prev:hover,
.lightbox-next:hover { background: rgba(255, 255, 255, 0.22); }
.lightbox-close { top: 20px; right: 20px; }
.lightbox-prev { left: 20px; top: 50%; transform: translateY(-50%); }
.lightbox-next { right: 20px; top: 50%; transform: translateY(-50%); }

@media (max-width: 720px) {
  .gallery-cap { opacity: 1; }
  .lightbox-prev { left: 8px; }
  .lightbox-next { right: 8px; }
}