/* --- CSS VARIABLES --- */
    :root {
      /* Palette Scientific */
      --primary-color: #0f172a;    /* Deep Navy */
      --secondary-color: #334155;  /* Slate */
      --accent-color: #3b82f6;     /* Electric Blue */
      --accent-gradient: linear-gradient(135deg, #3b82f6 0%, #06b6d4 100%);
      --bg-color: #f8fafc;         
      --card-bg: #ffffff;
      --text-color: #1e293b;
      --text-light: #64748b;
      
      /* Shadows & Radius */
      --shadow-sm: 0 4px 6px -1px rgba(0, 0, 0, 0.05);
      --shadow-md: 0 10px 30px -5px rgba(0, 0, 0, 0.08);
      --radius: 12px;
      
      /* Layout */
      --header-height: 80px;
      
      /* Typography */
      --font-body: 'Inter', sans-serif;
      --font-heading: 'Lora', serif; /* Formal Font */
    }

    * { margin: 0; padding: 0; box-sizing: border-box; }
    html { scroll-behavior: smooth; }
    body { font-family: var(--font-body); background-color: var(--bg-color); color: var(--text-color); line-height: 1.7; overflow-x: hidden; }
    
    a { text-decoration: none; color: inherit; transition: 0.3s; }
    ul { list-style: none; }
    img { max-width: 100%; display: block; height: auto; border-radius: var(--radius); }
    h1, h2, h3, h4 { font-family: var(--font-heading); color: var(--primary-color); }

    /* --- UTILITIES --- */
    .container { max-width: 1100px; margin: 0 auto; padding: 0 24px; }
    .section { padding: 100px 0; }
    
    .section__title {
      font-size: 2.5rem; text-align: center; margin-bottom: 1rem; position: relative;
    }
    .section__subtitle {
      text-align: center; color: var(--text-light); max-width: 600px; margin: 0 auto 4rem; font-size: 1rem;
    }

    .btn {
      display: inline-flex; align-items: center; gap: 8px; padding: 12px 28px;
      background: var(--primary-color); color: #fff; border-radius: 50px;
      font-weight: 500; border: none; cursor: pointer; transition: all 0.3s ease;
      box-shadow: var(--shadow-sm); font-family: var(--font-body);
    }
    .btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); background: var(--accent-color); }
    .btn--outline { background: transparent; border: 1px solid var(--primary-color); color: var(--primary-color); }
    .btn--outline:hover { background: var(--primary-color); color: #fff; }

    /* --- HEADER (Original Style Preserved) --- */
    .l-header {
      position: fixed; top: 0; left: 0; width: 100%; z-index: 1000;
      background: rgba(255, 255, 255, 0.85);
      backdrop-filter: blur(12px); /* Glassmorphism */
      border-bottom: 1px solid rgba(0,0,0,0.05);
      height: var(--header-height);
      display: flex; align-items: center;
    }
    .nav { width: 100%; display: flex; justify-content: space-between; align-items: center; }
    .nav__logo { font-weight: 700; font-size: 1.25rem; color: var(--primary-color); display: flex; align-items: center; gap: 5px; }
    .nav__list { display: flex; gap: 2.5rem; }
    .nav__link { font-weight: 500; color: var(--secondary-color); position: relative; font-size: 0.95rem; }
    .nav__link:hover { color: var(--accent-color); }
    .nav__link::after {
      content: ''; position: absolute; bottom: -4px; left: 0; width: 0; height: 2px;
      background: var(--accent-gradient); transition: 0.3s;
    }
    .nav__link:hover::after { width: 100%; }
    .nav__toggle { display: none; font-size: 1.5rem; cursor: pointer; }

    /* --- HERO SECTION --- */
    .hero {
      padding-top: 180px; padding-bottom: 100px; text-align: center;
      background: linear-gradient(180deg, #f8fafc 0%, #e2e8f0 100%);
    }
    .hero__overline {
      display: block; font-size: 0.85rem; font-weight: 700; letter-spacing: 2px;
      color: var(--accent-color); text-transform: uppercase; margin-bottom: 1.5rem;
    }
    .hero__title {
      font-size: 3.5rem; line-height: 1.2; margin-bottom: 1.5rem;
    }
    .hero__desc {
      font-size: 1.15rem; color: var(--text-light); max-width: 700px; margin: 0 auto 2.5rem; font-family: var(--font-heading); font-style: italic;
    }

    /* --- STATS SECTION (New) --- */
    .stats { padding: 40px 0; background: #fff; border-bottom: 1px solid #eee; }
    .stats__grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; text-align: center; }
    .stat__number { font-size: 2.5rem; font-weight: 700; color: var(--accent-color); display: block; }
    .stat__label { font-size: 0.9rem; color: var(--text-light); text-transform: uppercase; letter-spacing: 1px; }

    /* --- RESEARCH GRID (Enhanced) --- */
    .research-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 30px; }
    .research-card {
      background: var(--card-bg); border-radius: var(--radius); overflow: hidden;
      box-shadow: var(--shadow-sm); transition: 0.4s ease; border: 1px solid rgba(0,0,0,0.04);
      display: flex; flex-direction: column;
    }
    .research-card:hover { transform: translateY(-8px); box-shadow: var(--shadow-md); border-color: rgba(59, 130, 246, 0.3); }
    .card-img { height: 220px; overflow: hidden; }
    .card-img img { width: 100%; height: 100%; object-fit: cover; transition: 0.5s; }
    .research-card:hover .card-img img { transform: scale(1.05); }
    .card-content { padding: 2rem; display: flex; flex-direction: column; flex-grow: 1; }
    .card-tag { 
      font-size: 0.75rem; text-transform: uppercase; color: var(--accent-color); font-weight: 700; margin-bottom: 0.5rem; 
    }
    .card-title { font-size: 1.4rem; margin-bottom: 1rem; line-height: 1.3; }
    .card-desc { font-size: 0.95rem; color: var(--text-light); margin-bottom: 1.5rem; flex-grow: 1; }
    .card-footer { display: flex; justify-content: space-between; align-items: center; margin-top: auto; padding-top: 1rem; border-top: 1px solid #f1f5f9; }
    .read-more { font-weight: 600; font-size: 0.9rem; color: var(--primary-color); display: flex; align-items: center; gap: 5px; cursor: pointer; }
    .read-more:hover { color: var(--accent-color); gap: 8px; }

    /* --- ACADEMIC TIMELINE (New) --- */
    .timeline { position: relative; max-width: 800px; margin: 0 auto; }
    .timeline::after {
      content: ''; position: absolute; width: 2px; background-color: #e2e8f0;
      top: 0; bottom: 0; left: 50%; margin-left: -1px;
    }
    .timeline-item { padding: 10px 40px; position: relative; width: 50%; box-sizing: border-box; }
    .timeline-item.left { left: 0; text-align: right; }
    .timeline-item.right { left: 50%; }
    
    .timeline-content {
      padding: 20px 30px; background: white; border-radius: var(--radius); box-shadow: var(--shadow-sm); z-index: 1; position: relative;
    }
    .timeline-date { color: var(--accent-color); font-weight: 600; font-size: 0.9rem; margin-bottom: 5px; display: block; }
    .timeline-title { font-size: 1.2rem; margin-bottom: 5px; }
    .timeline-desc { font-size: 0.9rem; color: var(--text-light); }
    
    /* Dot on line */
    .timeline-dot {
      position: absolute; width: 16px; height: 16px; background-color: #fff;
      border: 4px solid var(--accent-color); border-radius: 50%; top: 25px; z-index: 10;
      right: -8px; /* For left items */
    }
    .timeline-item.right .timeline-dot { left: -8px; }

  /* ===== Publications spacing fix (Year + Text đều nhau) ===== */
.pub-item{
  display: grid;
  grid-template-columns: 140px 1fr;  /* cột năm cố định */
  column-gap: 24px;                 /* khoảng cách năm và chữ cố định */
  align-items: start;
}

.pub-year{
  width: 140px;
  min-width: 140px;
  text-align: right;                /* năm sát phần chữ, nhìn gọn và đều */
  white-space: nowrap;              /* tránh 2023–2024 bị xuống dòng */
  line-height: 1;
}

/* Mobile: xếp năm lên trên cho gọn */
@media (max-width: 650px){
  .pub-item{
    grid-template-columns: 1fr;
    row-gap: 10px;
  }
  .pub-year{
    width: auto;
    min-width: 0;
    text-align: left;
  }
}


    /* --- FOOTER --- */
    footer { background: var(--primary-color); color: #fff; padding: 60px 0; text-align: center; }
    .footer__socials { display: flex; justify-content: center; gap: 20px; margin-bottom: 20px; font-size: 1.5rem; }
    .footer__copy { color: #94a3b8; font-size: 0.9rem; }

    /* --- STORY MODAL (Full Screen) --- */
    .modal-overlay {
      position: fixed; inset: 0; background: rgba(15,23,42,0.6); backdrop-filter: blur(5px);
      z-index: 2000; opacity: 0; visibility: hidden; transition: 0.3s;
    }
    .modal-overlay.active { opacity: 1; visibility: visible; }
    
    .story-panel {
      position: fixed; bottom: 0; left: 0; width: 100%; height: 90vh;
      background: #fff; border-radius: 20px 20px 0 0; z-index: 2001;
      transform: translateY(100%); transition: transform 0.5s cubic-bezier(0.19, 1, 0.22, 1);
      overflow-y: auto; padding: 0; display: flex; flex-direction: column;
    }
    .story-panel.active { transform: translateY(0); }
    
    .story-nav {
      position: sticky; top: 0; background: rgba(255,255,255,0.9); backdrop-filter: blur(10px);
      padding: 15px 30px; display: flex; justify-content: space-between; align-items: center;
      border-bottom: 1px solid #eee; z-index: 10;
    }
    .story-close { font-size: 1.8rem; cursor: pointer; color: var(--text-color); }
    
    .story-body { max-width: 800px; margin: 0 auto; padding: 40px 24px 100px; }
    .story-hero-img { width: 100%; height: 400px; object-fit: cover; border-radius: var(--radius); margin-bottom: 30px; }
    .story-header h2 { font-size: 2.5rem; margin-bottom: 10px; }
    .story-meta { font-family: var(--font-body); color: var(--accent-color); font-weight: 600; margin-bottom: 30px; }
    .story-content p { margin-bottom: 20px; font-size: 1.1rem; color: #334155; text-align: justify; }
    .story-highlight {
      border-left: 4px solid var(--accent-color); padding-left: 20px; margin: 30px 0;
      font-style: italic; color: var(--primary-color); font-size: 1.2rem; font-family: var(--font-heading);
    }

    /* --- RESPONSIVE --- */
    @media (max-width: 768px) {
      .hero__title { font-size: 2.5rem; }
      .timeline::after { left: 31px; }
      .timeline-item { width: 100%; padding-left: 70px; padding-right: 25px; }
      .timeline-item.left, .timeline-item.right { left: 0; text-align: left; }
      .timeline-dot { left: 23px !important; } /* Fix dot position */
      .stats__grid { grid-template-columns: 1fr 1fr; }
      .nav__menu {
        position: fixed; top: var(--header-height); right: -100%; width: 80%; height: 100vh;
        background: #fff; padding: 2rem; transition: 0.3s; box-shadow: -2px 0 10px rgba(0,0,0,0.1);
      }
      .nav__menu.show-menu { right: 0; }
      .nav__list { flex-direction: column; }
      .nav__toggle { display: block; }
    }

    /* ===== TINH CHỈNH MENU: NHỎ GỌN & XANH CYAN ===== */
:root {
    --header-height: 4.5rem; /* Giảm chiều cao xuống cho gọn */
    --brand-blue: #00adef;   /* Màu xanh chính xác từ ảnh bạn gửi */
    --text-dark: #1e293b;
    --text-gray: #64748b;
}

.main-header {
    width: 100%;
    position: fixed;
    top: 0;
    left: 0;
    z-index: 1000;
    background: transparent;
    transition: all 0.3s ease;
}

/* Khi cuộn chuột */
.main-header.scrolled {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    height: 4rem;
    box-shadow: 0 2px 15px rgba(0, 0, 0, 0.05);
}

.nav-container {
    max-width: 100%;
    padding: 0 3rem; /* Khoảng cách lề vừa phải */
    height: 100%;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* LOGO NHỎ GỌN */
.nav-logo {
    font-family: 'Be Vietnam Pro', sans-serif;
    font-size: 1.6rem; /* Giảm size logo */
    font-weight: 800;
    color: var(--text-dark);
    text-decoration: none;
    letter-spacing: -0.5px;
}

.brand-blue {
    color: var(--brand-blue);
}

/* MENU LINKS THANH THOÁT */
.nav-list {
    display: flex;
    column-gap: 2.5rem; /* Khoảng cách các mục vừa đủ */
    list-style: none;
}

.nav-link {
    font-family: 'Inter', sans-serif;
    font-size: 0.9rem; /* Chữ nhỏ lại xíu cho sang */
    font-weight: 600;
    color: var(--text-gray);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    text-decoration: none;
    position: relative;
    transition: 0.3s;
}

.nav-link:hover, .active-link {
    color: var(--brand-blue);
}

/* Hiệu ứng gạch chân đơn giản màu xanh */
.nav-link::after {
    content: "";
    position: absolute;
    bottom: -6px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--brand-blue);
    transition: width 0.3s ease;
}

.nav-link:hover::after, .active-link::after {
    width: 100%;
}

.stats__grid{
  display: flex;
  justify-content: center;   /* căn giữa cả 3 item */
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;           /* xuống dòng đẹp trên mobile */
  text-align: center;
}

.stat-item{
  min-width: 180px;          /* tùy chỉnh */
}


/* MOBILE RESPONSIVE */
@media screen and (max-width: 767px) {
    .nav-container { padding: 0 1.5rem; }
    
    .nav-menu {
        position: fixed;
        top: -100%;
        left: 0;
        width: 100%;
        background: white;
        padding: 4rem 0;
        text-align: center;
        transition: 0.4s;
        box-shadow: 0 4px 10px rgba(0,0,0,0.1);
    }
    
    .nav-list { flex-direction: column; row-gap: 2rem; }
    .nav-toggle { font-size: 1.5rem; color: var(--text-dark); cursor: pointer; }
    .nav-close { position: absolute; top: 1rem; right: 1.5rem; font-size: 2rem; cursor: pointer; }
    .show-menu { top: 0 !important; }
}

@media screen and (min-width: 768px) {
    .nav-toggle, .nav-close { display: none; }
}


/* =========================
   Publications -> Card style
   ========================= */
.publications-list{
  display: flex;
  flex-direction: column;
  gap: 18px; /* khoảng cách giữa các card */
}

.pub-item{
  background: #fff;
  border: 1px solid rgba(15, 23, 42, 0.10);
  border-radius: 16px;
  padding: 22px 22px;
  box-shadow: 0 10px 28px rgba(15, 23, 42, 0.06);

  /* giữ layout năm + chữ đều nhau như bạn vừa chỉnh */
  display: grid;
  grid-template-columns: 140px 1fr;
  column-gap: 24px;
  align-items: start;
}

/* cột năm gọn, không xuống dòng */
.pub-year{
  width: 140px;
  min-width: 140px;
  text-align: right;
  white-space: nowrap;
  color: rgba(15, 23, 42, 0.55);
  font-weight: 700;
  letter-spacing: 0.5px;
}

/* title + meta đẹp hơn */
.pub-content h3,
.pub-title{
  margin: 0 0 8px 0;
}

.pub-meta{
  margin: 0 0 10px 0;
  color: rgba(15, 23, 42, 0.65);
}

/* nút PDF nhìn giống button */
.pub-actions a,
.pub-pdf{
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 10px;
  border: 1px solid rgba(59, 130, 246, 0.35);
  color: #2563eb;
  background: rgba(59, 130, 246, 0.06);
  font-weight: 600;
  text-decoration: none;
}

.pub-actions a:hover,
.pub-pdf:hover{
  background: rgba(59, 130, 246, 0.12);
}

/* Mobile: năm lên trên, card gọn */
@media (max-width: 650px){
  .pub-item{
    grid-template-columns: 1fr;
    row-gap: 10px;
    padding: 18px 16px;
  }
  .pub-year{
    width: auto;
    min-width: 0;
    text-align: left;
  }
}