/* ============================================================
   Personal Homepage — Custom Styles
   Bootstrap 5 위에 덧씌우는 커스텀 스타일.
   색상/폰트를 바꾸고 싶다면 아래 :root 변수만 수정하세요.
   ============================================================ */

:root {
  --accent-color: #ff5a1f;       /* 메인 강조색 (버튼, 제목 하이라이트) */
  --accent-dark: #d94a18;
  --bg-dark: #1a1a1a;            /* Hero 배경 */
  --text-dark: #212529;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

/* ----- Base ----- */
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  color: var(--text-dark);
  line-height: 1.7;
}

/* ----- Navbar ----- */
#mainNav {
  background-color: rgba(26, 26, 26, 0.0);
  transition: background-color 0.3s ease, padding 0.3s ease;
  padding: 1.25rem 0;
}
#mainNav.scrolled {
  background-color: rgba(26, 26, 26, 0.95);
  padding: 0.6rem 0;
  backdrop-filter: blur(8px);
}
#mainNav .navbar-brand { letter-spacing: 2px; }
#mainNav .nav-link {
  color: rgba(255, 255, 255, 0.85) !important;
  font-weight: 500;
  margin: 0 0.5rem;
}
#mainNav .nav-link:hover,
#mainNav .nav-link.active { color: var(--accent-color) !important; }

/* ----- Hero ----- */
.hero {
  background: linear-gradient(135deg, #1a1a1a 0%, #2d2d2d 100%);
  color: #fff;
  padding-top: 6rem;
}
.hero .display-2 { line-height: 1.1; }
.text-accent { color: var(--accent-color) !important; }

/* ----- Buttons ----- */
.btn-accent {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
  color: #fff;
}
.btn-accent:hover,
.btn-accent:focus {
  background-color: var(--accent-dark);
  border-color: var(--accent-dark);
  color: #fff;
}

/* ----- Section ----- */
.section-padding { padding: 6rem 0; }
.section-title {
  font-weight: 800;
  font-size: 2.5rem;
  margin-bottom: 0.5rem;
  position: relative;
  display: inline-block;
}
.section-title::after {
  content: '';
  display: block;
  width: 60px;
  height: 4px;
  background: var(--accent-color);
  margin: 0.75rem auto 0;
  border-radius: 2px;
}
.section-subtitle { color: #6c757d; font-size: 1.1rem; }

/* ----- About ----- */
.profile-img {
  width: 240px;
  height: 240px;
  object-fit: cover;
  border: 6px solid #fff;
}

/* ----- Research cards ----- */
.research-icon { font-size: 3rem; line-height: 1; }
.card { transition: transform 0.25s ease, box-shadow 0.25s ease; }
.card:hover { transform: translateY(-6px); box-shadow: 0 1rem 2rem rgba(0,0,0,0.1) !important; }

/* ----- Publications ----- */
.publication-list { padding-left: 1.25rem; }
.pub-title { font-size: 1.05rem; }

/* ----- Contact / Social ----- */
.social-links a {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: #f1f1f1;
  color: var(--text-dark);
  font-size: 1.4rem;
  margin: 0 0.35rem;
  transition: all 0.25s ease;
}
.social-links a:hover {
  background: var(--accent-color);
  color: #fff;
  transform: translateY(-3px);
}

/* ----- Timeline (Education / Experience) ----- */
.timeline-list {
  position: relative;
  padding-left: 2rem;
  border-left: 3px solid var(--accent-color);
}
.timeline-item {
  position: relative;
  padding: 0.25rem 0 1.75rem 0.75rem;
}
.timeline-item::before {
  content: '';
  position: absolute;
  left: -2.55rem;
  top: 0.5rem;
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent-color);
  border: 3px solid #fff;
  box-shadow: 0 0 0 1px var(--accent-color);
}
.timeline-item h5 { font-size: 1.1rem; }

/* ----- Project / Award list ----- */
.project-list {
  list-style: none;
  padding-left: 0;
}
.project-list li {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.65rem 0;
  border-bottom: 1px solid #e9ecef;
}
.project-list li:last-child { border-bottom: none; }
.project-list li > span:first-child { flex: 1; }
@media (max-width: 576px) {
  .project-list li { flex-direction: column; gap: 0.25rem; }
}

/* ----- Footer ----- */
footer { background: #f8f9fa; }

/* ----- Responsive tweaks ----- */
@media (max-width: 768px) {
  .hero .display-2 { font-size: 3rem; }
  .section-padding { padding: 4rem 0; }
  .section-title { font-size: 2rem; }
  .profile-img { width: 180px; height: 180px; }
}