/* -------------------------------------------------
   Yoonsik Park — minimal GitHub Pages theme
   Tone: white / gray / black
   Font stack starts with Calibri.
-------------------------------------------------- */

:root {
  --bg: #f7f7f5;
  --surface: rgba(255, 255, 255, 0.84);
  --surface-strong: #ffffff;
  --text: #141414;
  --text-soft: #4f4f4b;
  --text-faint: #82827b;
  --line: rgba(20, 20, 20, 0.08);
  --line-strong: rgba(20, 20, 20, 0.15);
  --shadow-soft: 0 14px 34px rgba(20, 20, 20, 0.04);
  --shadow-lift: 0 18px 44px rgba(20, 20, 20, 0.07);
  --radius-xl: 28px;
  --radius-lg: 22px;
  --radius-md: 16px;
  --radius-sm: 12px;
  --site-width: 1080px;
  --transition: 180ms ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  min-width: 320px;
  font-family: Calibri, Candara, "Segoe UI", Segoe, Optima, Arial, sans-serif;
  color: var(--text);
  background: linear-gradient(180deg, #fbfbfa 0%, var(--bg) 100%);
  line-height: 1.7;
  letter-spacing: 0.004em;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

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

a {
  color: inherit;
  text-decoration: none;
}

p,
li,
dd {
  color: var(--text-soft);
}

strong {
  color: var(--text);
}

::selection {
  background: rgba(20, 20, 20, 0.12);
  color: var(--text);
}

.skip-link {
  position: absolute;
  top: -48px;
  left: 16px;
  z-index: 999;
  padding: 10px 14px;
  border-radius: 999px;
  background: var(--text);
  color: #fff;
  transition: top var(--transition);
}

.skip-link:focus {
  top: 16px;
}

.container {
  width: min(calc(100% - 40px), var(--site-width));
  margin: 0 auto;
}

.page-shell {
  min-height: 100vh;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(251, 251, 250, 0.74);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
  transition:
    background-color var(--transition),
    border-color var(--transition),
    box-shadow var(--transition);
}

.site-header.is-scrolled {
  border-color: var(--line);
  box-shadow: 0 8px 20px rgba(20, 20, 20, 0.03);
}

.header-inner {
  min-height: 68px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.brand {
  font-size: 1rem;
  font-weight: 700;
  letter-spacing: 0.01em;
  color: var(--text);
  white-space: nowrap;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 6px;
  overflow-x: auto;
  padding-bottom: 2px;
  scrollbar-width: none;
}

.site-nav::-webkit-scrollbar {
  display: none;
}

.nav-link {
  padding: 8px 12px;
  border-radius: 999px;
  color: var(--text-faint);
  font-size: 0.95rem;
  white-space: nowrap;
  transition:
    color var(--transition),
    background-color var(--transition);
}

.nav-link:hover,
.nav-link:focus-visible,
.nav-link.is-active {
  color: var(--text);
  background: rgba(20, 20, 20, 0.05);
}

.main-content {
  padding: 34px 0 84px;
}

section {
  scroll-margin-top: 92px;
}

.section {
  margin-top: 72px;
}

.section-first {
  margin-top: 8px;
}

.section-title {
  margin: 0 0 22px;
  font-size: clamp(1.65rem, 2.4vw, 2.15rem);
  line-height: 1.15;
  letter-spacing: -0.03em;
}

.about-layout {
  display: grid;
  grid-template-columns: 240px minmax(0, 1fr);
  gap: 40px;
  align-items: start;
}

.about-photo-column {
  position: sticky;
  top: 108px;
}

.photo-frame {
  overflow: hidden;
  aspect-ratio: 4 / 5;
  border-radius: 28px;
  background: linear-gradient(180deg, #efefec 0%, #e6e6e1 100%);
  border: 1px solid var(--line);
  box-shadow: var(--shadow-soft);
}

.profile-photo {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.about-links {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 16px;
  margin-top: 14px;
}

.about-links a {
  position: relative;
  font-size: 0.94rem;
  color: var(--text-faint);
  padding-bottom: 2px;
}

.about-links a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
  height: 1px;
  background: currentColor;
  opacity: 0.35;
  transform: scaleX(0.5);
  transform-origin: left;
  transition:
    transform var(--transition),
    opacity var(--transition),
    color var(--transition);
}

.about-links a:hover,
.about-links a:focus-visible {
  color: var(--text);
}

.about-links a:hover::after,
.about-links a:focus-visible::after {
  transform: scaleX(1);
  opacity: 0.8;
}

.page-title {
  margin: 0;
  font-size: clamp(2.65rem, 5vw, 4rem);
  line-height: 1.02;
  letter-spacing: -0.05em;
}

.page-subtitle {
  margin: 10px 0 22px;
  font-size: 1.02rem;
  color: var(--text-faint);
}

.about-copy {
  max-width: 760px;
}

.about-copy p {
  margin: 0 0 16px;
  font-size: 1.04rem;
}

.about-copy p:last-child {
  margin-bottom: 0;
}

.about-meta {
  margin: 26px 0 0;
  padding-top: 20px;
  border-top: 1px solid var(--line);
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px 22px;
}

.about-meta div {
  display: grid;
  gap: 4px;
}

.about-meta dt {
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  color: var(--text-faint);
}

.about-meta dd {
  margin: 0;
  font-size: 0.95rem;
  color: var(--text);
}

.simple-list {
  border-top: 1px solid var(--line);
}

.news-row,
.entry,
.simple-list-item {
  border-bottom: 1px solid var(--line);
}

.news-row {
  display: grid;
  grid-template-columns: 112px minmax(0, 1fr);
  gap: 18px;
  align-items: start;
  padding: 14px 12px;
  margin: 0 -12px;
  border-radius: 16px;
  transition:
    background-color var(--transition),
    transform var(--transition);
}

.news-row:hover {
  background: rgba(20, 20, 20, 0.03);
}

.row-date {
  font-size: 0.94rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: 0.01em;
}

.row-body {
  color: var(--text-soft);
}

.entry {
  padding: 20px 0 22px;
}

.entry-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 20px;
}

.entry-title {
  margin: 0;
  font-size: 1.16rem;
  line-height: 1.28;
  color: var(--text);
}

.entry-subtitle {
  margin: 4px 0 0;
  font-size: 0.97rem;
  color: var(--text-faint);
}

.entry-date {
  min-width: fit-content;
  font-size: 0.92rem;
  color: var(--text-faint);
  white-space: nowrap;
}

.entry-points {
  margin: 12px 0 0;
  padding-left: 18px;
}

.entry-points li + li {
  margin-top: 6px;
}

.publication-item {
  padding: 20px 0 22px;
}

.publication-authors {
  margin: 10px 0 0;
}

.publication-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 14px;
}

.meta-chip,
.tag {
  display: inline-flex;
  align-items: center;
  min-height: 32px;
  padding: 0 11px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.7);
  color: var(--text);
  font-size: 0.88rem;
}

.project-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.project-card {
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: var(--radius-lg);
  background: var(--surface);
  box-shadow: var(--shadow-soft);
  transition:
    transform var(--transition),
    box-shadow var(--transition),
    border-color var(--transition),
    background-color var(--transition);
}

.project-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lift);
  border-color: var(--line-strong);
  background: var(--surface-strong);
}

.project-card h3 {
  margin: 0;
  font-size: 1.12rem;
  line-height: 1.3;
}

.project-meta {
  margin: 8px 0 0;
  font-size: 0.93rem;
  color: var(--text-faint);
}

.project-card p {
  margin: 12px 0 0;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
}

.site-footer {
  padding: 0 0 34px;
}

.footer-inner {
  padding-top: 18px;
  border-top: 1px solid var(--line);
}

.footer-inner p {
  margin: 0;
  color: var(--text-faint);
  font-size: 0.93rem;
}

.js .reveal {
  opacity: 0;
  transform: translateY(14px);
  transition:
    opacity 560ms ease,
    transform 560ms cubic-bezier(0.2, 0.75, 0.2, 1);
}

.js .reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

@media (max-width: 980px) {
  .about-layout,
  .project-grid {
    grid-template-columns: 1fr;
  }

  .about-photo-column {
    position: static;
    max-width: 260px;
  }
}

@media (max-width: 760px) {
  .container {
    width: min(calc(100% - 24px), var(--site-width));
  }

  .header-inner {
    min-height: 60px;
    flex-direction: column;
    align-items: flex-start;
    justify-content: center;
    gap: 10px;
    padding: 10px 0;
  }

  .site-nav {
    width: 100%;
  }

  .main-content {
    padding: 20px 0 64px;
  }

  .section {
    margin-top: 56px;
  }

  .section-first {
    margin-top: 2px;
  }

  .news-row {
    grid-template-columns: 1fr;
    gap: 4px;
  }

  .entry-head {
    flex-direction: column;
    gap: 8px;
  }

  .about-meta {
    grid-template-columns: 1fr;
    gap: 12px;
  }
}

@media (max-width: 560px) {
  .page-title {
    font-size: 2.35rem;
  }

  .section-title {
    margin-bottom: 18px;
  }

  .photo-frame {
    border-radius: 24px;
  }

  .project-card {
    padding: 18px;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }

  .js .reveal {
    opacity: 1;
    transform: none;
  }
}