/* =========================================================
   Koa Shen — Portfolio
   Design tokens
   ========================================================= */
:root {
  --bg:        #0b0f14;
  --bg-alt:    #0f151c;
  --surface:   #141b24;
  --surface-2: #1a222d;
  --line:      #243040;
  --text:      #e6edf5;
  --text-dim:  #9aa9bd;
  --text-mute: #6b7c92;
  --accent:    #4ea1ff;
  --accent-2:  #5ee0c0;
  --warn:      #ffd166;
  --radius:    14px;
  --radius-sm: 9px;
  --wrap:      1140px;
  --ease:      cubic-bezier(.22,.61,.36,1);
  --copy-leading: 1.72;
  --paragraph-space: 1.3rem;
  --section-space: 2.1rem;
  --heading-copy-space: .9rem;
  --shadow:    0 18px 50px -20px rgba(0,0,0,.75);
  --font:      'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --mono:      'JetBrains Mono', ui-monospace, 'Cascadia Code', monospace;
}

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

html { scroll-behavior: smooth; scroll-padding-top: 86px; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font);
  font-size: 16px;
  line-height: var(--copy-leading);
  -webkit-font-smoothing: antialiased;
}

img { max-width: 100%; display: block; }
a { color: var(--accent); text-decoration: none; }
a:hover { color: var(--accent-2); }

h1, h2, h3, h4 { line-height: 1.15; margin: 0 0 .5em; letter-spacing: -.02em; }

.wrap { width: min(100% - 2.5rem, var(--wrap)); margin-inline: auto; }

.skip-link {
  position: absolute; left: -9999px; top: 0; z-index: 999;
  background: var(--accent); color: #001322; padding: .6rem 1rem; border-radius: 0 0 8px 0;
}
.skip-link:focus { left: 0; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 4px; }

/* =========================================================
   Buttons
   ========================================================= */
.btn {
  display: inline-flex; align-items: center; gap: .5rem;
  padding: .7rem 1.3rem;
  background: var(--accent);
  color: #04121f;
  font-weight: 600; font-size: .93rem;
  border: 1px solid transparent;
  border-radius: 999px;
  font-family: inherit;
  cursor: pointer;
  transition: transform .18s var(--ease), box-shadow .18s var(--ease), background .18s var(--ease);
  white-space: nowrap;
}
.btn:hover {
  color: #04121f;
  background: #6fb4ff;
  transform: translateY(-2px);
  box-shadow: 0 10px 26px -10px rgba(78,161,255,.7);
}
.btn--ghost { background: transparent; color: var(--text); border-color: var(--line); }
.btn--ghost:hover { background: var(--surface-2); color: var(--text); box-shadow: none; border-color: var(--accent); }
.btn--sm { padding: .45rem 1rem; font-size: .85rem; }

/* =========================================================
   Nav
   ========================================================= */
.nav {
  position: sticky; top: 0; z-index: 100;
  backdrop-filter: blur(14px);
  background: rgba(11,15,20,.72);
  border-bottom: 1px solid transparent;
  transition: border-color .3s var(--ease), background .3s var(--ease);
}
.nav.is-stuck { border-bottom-color: var(--line); background: rgba(11,15,20,.9); }

.nav__inner {
  width: min(100% - 2.5rem, var(--wrap));
  margin-inline: auto;
  height: 68px;
  display: flex; align-items: center; justify-content: space-between;
}
.nav__brand {
  font-weight: 800; font-size: 1.25rem; letter-spacing: -.04em; color: var(--text);
}
.nav__brand .dot { color: var(--accent); }

.nav__links { display: flex; align-items: center; gap: 1.6rem; }
.nav__links a {
  color: var(--text-dim); font-size: .92rem; font-weight: 500;
  transition: color .18s var(--ease);
}
.nav__links a:hover, .nav__links a.is-active { color: var(--text); }
.nav__links a.btn { color: #04121f; }

.nav__toggle {
  display: none;
  width: 42px; height: 38px;
  background: none; border: 1px solid var(--line); border-radius: 9px;
  cursor: pointer; padding: 9px 10px;
  flex-direction: column; justify-content: space-between;
}
.nav__toggle span { display: block; height: 2px; background: var(--text); border-radius: 2px; transition: .25s var(--ease); }
.nav__toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(8px) rotate(45deg); }
.nav__toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav__toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-8px) rotate(-45deg); }

/* =========================================================
   Hero
   ========================================================= */
.hero { position: relative; padding: clamp(3.5rem, 9vw, 7rem) 0 3.5rem; overflow: hidden; }
.hero__glow {
  position: absolute; inset: -30% -10% auto -10%; height: 620px;
  background:
    radial-gradient(50% 60% at 22% 35%, rgba(78,161,255,.20), transparent 70%),
    radial-gradient(40% 55% at 78% 25%, rgba(94,224,192,.13), transparent 70%);
  filter: blur(10px); pointer-events: none;
}
.hero__grid {
  position: relative;
  display: grid; grid-template-columns: 1.15fr .85fr; gap: clamp(2rem, 5vw, 4rem);
  align-items: center;
}
.eyebrow {
  font-family: var(--mono); font-size: .8rem; letter-spacing: .12em; text-transform: uppercase;
  color: var(--accent-2); margin: 0 0 1rem;
}
.hero__name { font-size: clamp(2.6rem, 7vw, 4.4rem); font-weight: 800; margin-bottom: .15em; }
.hero__role { font-size: clamp(1.05rem, 2.2vw, 1.35rem); color: var(--text-dim); font-weight: 500; margin: 0 0 1.1rem; }
.hero__tagline { color: var(--text-dim); max-width: 54ch; font-size: 1.03rem; margin: 0 0 2rem; }
.hero__cta { display: flex; gap: .8rem; flex-wrap: wrap; margin-bottom: 1.6rem; }

.hero__links { list-style: none; display: flex; gap: 1.4rem; padding: 0; margin: 0; flex-wrap: wrap; font-size: .9rem; }
.hero__links a { color: var(--text-dim); border-bottom: 1px solid transparent; }
.hero__links a:hover { color: var(--accent); border-bottom-color: var(--accent); }

.hero__media img,
.hero__media .ph { width: 100%; aspect-ratio: 4/5; border-radius: var(--radius); object-fit: cover; }

.hero__stats {
  position: relative;
  display: grid; grid-template-columns: repeat(4, 1fr); gap: 1px;
  background: var(--line); border: 1px solid var(--line); border-radius: var(--radius);
  overflow: hidden; margin-top: clamp(2.5rem, 6vw, 4rem);
}
.stat { background: var(--bg-alt); padding: 1.3rem 1.4rem; }
.stat__v { font-size: 1.45rem; font-weight: 700; letter-spacing: -.02em; }
.stat__l { font-size: .78rem; color: var(--text-mute); text-transform: uppercase; letter-spacing: .09em; }

/* =========================================================
   Sections
   ========================================================= */
.section { padding: clamp(3.5rem, 8vw, 6.5rem) 0; }
.section--alt { background: var(--bg-alt); border-block: 1px solid var(--line); }

.section__title {
  display: flex; align-items: baseline; gap: .8rem;
  font-size: clamp(1.6rem, 3.6vw, 2.2rem); font-weight: 700; margin-bottom: .6rem;
}
.section__num { font-family: var(--mono); font-size: .9rem; color: var(--accent); font-weight: 500; }
.section__lede { color: var(--text-dim); max-width: 62ch; margin: 0 0 2.5rem; }
.section__title + .about,
.section__title + .timeline,
.section__title + .skills { margin-top: 2.2rem; }

/* =========================================================
   About + Education
   ========================================================= */
.about { max-width: 68ch; }
.about p { color: var(--text-dim); margin: 0 0 var(--paragraph-space); }

.edu { margin-top: 2.8rem; display: grid; gap: 1.2rem; }
.edu__card {
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.5rem 1.7rem;
}
.edu__top { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; align-items: baseline; }
.edu__school { font-size: 1.12rem; font-weight: 700; margin: 0; }
.edu__meta { font-family: var(--mono); font-size: .82rem; color: var(--text-mute); }
.edu__degree { color: var(--accent-2); font-weight: 500; margin: .2rem 0 .1rem; }
.edu__gpa {
  display: inline-block; font-family: var(--mono); font-size: .8rem;
  background: rgba(94,224,192,.1); color: var(--accent-2);
  border: 1px solid rgba(94,224,192,.28); border-radius: 999px; padding: .15rem .7rem; margin-bottom: .8rem;
}
.edu ul { margin: 0; padding-left: 1.15rem; color: var(--text-dim); font-size: .93rem; }
.edu li { margin-bottom: .35rem; }

/* =========================================================
   Projects
   ========================================================= */
.projects { display: grid; grid-template-columns: repeat(auto-fill, minmax(330px, 1fr)); gap: 1.5rem; }

.card {
  display: flex; flex-direction: column;
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); overflow: hidden; color: inherit;
  transition: transform .25s var(--ease), border-color .25s var(--ease), box-shadow .25s var(--ease);
}
.card:hover {
  transform: translateY(-5px); border-color: var(--accent);
  box-shadow: var(--shadow); color: inherit;
}
.card--feature { grid-column: span 2; }

.card__media { position: relative; aspect-ratio: 16/9; overflow: hidden; background: var(--surface-2); }
.card__media img { width: 100%; height: 100%; object-fit: cover; transition: transform .5s var(--ease); }
.card__media--compact img { object-fit: contain; padding: .65rem; }
.card:hover .card__media img { transform: scale(1.04); }
.card:hover .card__media--compact img { transform: none; }

.card__body { padding: 1.4rem 1.5rem 1.6rem; display: flex; flex-direction: column; flex: 1; }
.card__org { font-family: var(--mono); font-size: .76rem; color: var(--accent); letter-spacing: .06em; text-transform: uppercase; }
.card__title { font-size: 1.16rem; font-weight: 700; margin: .45rem 0 .55rem; }
.card__summary { color: var(--text-dim); font-size: .93rem; margin: 0 0 1.1rem; flex: 1; }
.card__more { font-size: .88rem; font-weight: 600; color: var(--accent); }

.tags { display: flex; flex-wrap: wrap; gap: .4rem; margin-bottom: 1.1rem; }
.tag {
  font-family: var(--mono); font-size: .72rem;
  background: var(--surface-2); border: 1px solid var(--line); color: var(--text-dim);
  border-radius: 6px; padding: .2rem .55rem;
}

/* =========================================================
   Timeline
   ========================================================= */
.timeline { position: relative; padding-left: 1.9rem; }
.timeline::before {
  content: ''; position: absolute; left: 5px; top: 8px; bottom: 8px; width: 2px;
  background: linear-gradient(var(--accent), var(--line));
}
.tl { position: relative; padding-bottom: 2.6rem; }
.tl:last-child { padding-bottom: 0; }
.tl::before {
  content: ''; position: absolute; left: -1.9rem; top: .55rem;
  width: 12px; height: 12px; border-radius: 50%;
  background: var(--bg); border: 2px solid var(--accent);
}
.tl__top { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; align-items: baseline; }
.tl__role { font-size: 1.1rem; font-weight: 700; margin: 0; }
.tl__org { color: var(--accent-2); font-weight: 500; }
.tl__meta { font-family: var(--mono); font-size: .8rem; color: var(--text-mute); }
.tl__badge {
  font-family: var(--mono); font-size: .68rem; text-transform: uppercase; letter-spacing: .08em;
  border-radius: 999px; padding: .1rem .6rem; margin-left: .5rem; vertical-align: middle;
  border: 1px solid var(--line); color: var(--text-mute);
}
.tl__badge--paid { color: var(--accent); border-color: rgba(78,161,255,.4); background: rgba(78,161,255,.08); }
.tl ul { margin: .8rem 0 0; padding-left: 1.15rem; color: var(--text-dim); font-size: .94rem; }
.tl li { margin-bottom: .45rem; }

/* =========================================================
   Skills
   ========================================================= */
.skills { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.5rem; }
.skillgroup {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 1.5rem 1.6rem;
}
.skillgroup h3 { font-size: 1rem; letter-spacing: .04em; text-transform: uppercase; color: var(--accent); font-family: var(--mono); font-weight: 500; margin-bottom: 1.2rem; }
.skill { margin-bottom: 1rem; }
.skill:last-child { margin-bottom: 0; }
.skill__top { display: flex; justify-content: space-between; font-size: .9rem; margin-bottom: .35rem; }
.skill__lvl { font-family: var(--mono); font-size: .75rem; color: var(--text-mute); }
.skill__bar { height: 5px; background: var(--surface-2); border-radius: 99px; overflow: hidden; }
.skill__fill {
  height: 100%; width: 0; border-radius: 99px;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width 1s var(--ease);
}

/* =========================================================
   Contact
   ========================================================= */
.contact { text-align: center; }
.contact .section__title { justify-content: center; }
.contact__lede { color: var(--text-dim); margin: 0 auto 2rem; max-width: 50ch; }
.contact__links { display: flex; justify-content: center; gap: 1rem; flex-wrap: wrap; }

/* =========================================================
   Footer
   ========================================================= */
.footer { border-top: 1px solid var(--line); padding: 2rem 0; background: var(--bg-alt); }
.footer__inner { display: flex; justify-content: space-between; gap: 1rem; flex-wrap: wrap; font-size: .85rem; color: var(--text-mute); }

/* =========================================================
   Placeholder tiles (missing images)
   ========================================================= */
.ph {
  display: flex; align-items: center; justify-content: center; text-align: center;
  min-height: 100%; padding: 1.5rem;
  background:
    repeating-linear-gradient(45deg, rgba(255,209,102,.07) 0 12px, transparent 12px 24px),
    var(--surface-2);
  border: 1px dashed rgba(255,209,102,.45);
  border-radius: var(--radius);
  font-family: var(--mono); font-size: .76rem; color: var(--warn);
  line-height: 1.5; word-break: break-word;
}
.card__media .ph { border-radius: 0; border-width: 0 0 1px; }

/* =========================================================
   FILLER highlighting — remove this block once content is final
   ========================================================= */
.filler {
  background: rgba(255,209,102,.11);
  border-left: 3px solid var(--warn);
  border-radius: 4px;
  padding: .2rem .55rem;
  color: #f0d9a0;
  display: inline-block;
}
.filler::before {
  content: 'NEEDS CONTENT';
  font-family: var(--mono); font-size: .62rem; letter-spacing: .1em;
  background: var(--warn); color: #2a1f00;
  border-radius: 3px; padding: .05rem .38rem; margin-right: .5rem;
  vertical-align: middle;
}
li.filler { display: list-item; margin-left: 0; }

/* =========================================================
   Scroll reveal
   ========================================================= */
.reveal { opacity: 0; transform: translateY(22px); transition: opacity .6s var(--ease), transform .6s var(--ease); }
.reveal.is-in { opacity: 1; transform: none; }

/* =========================================================
   Project detail page
   ========================================================= */
.detail { padding: clamp(2.5rem, 6vw, 4.5rem) 0; }
.detail__topline {
  display: flex; flex-wrap: wrap; align-items: baseline;
  gap: .75rem 1.25rem; margin-bottom: 2rem;
}
.back { font-family: var(--mono); font-size: .85rem; display: inline-block; }
.detail__org { font-family: var(--mono); font-size: .8rem; color: var(--accent); text-transform: uppercase; letter-spacing: .08em; }
.detail__title { font-size: clamp(1.9rem, 5vw, 3rem); font-weight: 800; margin: .4rem 0 .6rem; }
.detail__summary { color: var(--text-dim); font-size: 1.06rem; max-width: 68ch; margin: 0 0 var(--paragraph-space); }
.detail__cover { margin: 2.5rem 0; border-radius: var(--radius); overflow: hidden; border: 1px solid var(--line); }
.detail__cover img { width: 100%; aspect-ratio: 16/9; object-fit: cover; }
.detail__cover .ph { aspect-ratio: 16/9; }
.detail__cover--compact { max-width: 760px; margin-inline: auto; background: var(--surface-2); }
.detail__cover--compact img { aspect-ratio: auto; max-height: 520px; object-fit: contain; }

.detail__body { display: grid; grid-template-columns: minmax(0, 1fr) 260px; gap: 3rem; align-items: start; }
.detail__sections { min-width: 0; }
.detail__sections h3 {
  font-size: 1.15rem; margin-top: var(--section-space); margin-bottom: var(--heading-copy-space); padding-top: 1.1rem; border-top: 1px solid var(--line);
}
.detail__sections section:first-child > h3 { margin-top: 0; border-top: 0; padding-top: 0; }
.detail__sections p { color: var(--text-dim); margin: 0; line-height: var(--copy-leading); }
.project-video video {
  display: block;
  width: 100%;
  max-width: 100%;
  max-height: min(72vh, 640px);
  background: #05080b;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
}

.detail__aside {
  position: sticky; top: 92px;
  background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 1.3rem 1.4rem;
}
.detail__aside h4 { font-family: var(--mono); font-size: .75rem; text-transform: uppercase; letter-spacing: .1em; color: var(--text-mute); margin-bottom: .7rem; }
.detail__aside + * { margin-top: 0; }

.gallery { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1rem; margin-top: 1.2rem; }
.gallery figure { margin: 0; border-radius: var(--radius-sm); overflow: hidden; border: 1px solid var(--line); }
.gallery img { aspect-ratio: 4/3; object-fit: cover; width: 100%; }
.gallery .ph { aspect-ratio: 4/3; border-radius: var(--radius-sm); }
.gallery--compact { grid-template-columns: repeat(auto-fit, minmax(220px, 280px)); justify-content: center; }
.gallery--compact img { aspect-ratio: auto; max-height: 240px; object-fit: contain; background: var(--surface-2); }

.notfound { text-align: center; padding: 6rem 0; }

/* =========================================================
   Responsive
   ========================================================= */
@media (max-width: 900px) {
  .hero__grid { grid-template-columns: 1fr; }
  .hero__media { order: -1; max-width: 320px; }
  .hero__stats { grid-template-columns: repeat(2, 1fr); }
  .card--feature { grid-column: span 1; }
  .detail__body { grid-template-columns: minmax(0, 1fr); }
  .detail__aside { position: static; }
}

@media (max-width: 720px) {
  .about p { margin-bottom: calc(var(--paragraph-space) + .2rem); }
  .detail__topline { flex-direction: column; align-items: flex-start; gap: .75rem; margin-bottom: 1.5rem; }
  .detail__sections { --section-space: 2.25rem; --heading-copy-space: 1rem; }
  .detail__sections p { line-height: 1.78; }
  .nav__toggle { display: flex; }
  .nav__links {
    position: absolute; top: 68px; left: 0; right: 0;
    flex-direction: column; align-items: flex-start; gap: 0;
    background: var(--bg-alt); border-bottom: 1px solid var(--line);
    padding: .5rem 1.25rem 1.25rem;
    display: none;
  }
  .nav__links.is-open { display: flex; }
  .nav__links a { padding: .7rem 0; width: 100%; }
  .nav__links a.btn { margin-top: .6rem; width: auto; }
  .projects { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; }
}