/* ====== Base / Theme ====== */
:root{
  --bg:#f7f9fc;
  --card:#ffffff;
  --ink:#0f172a;
  --muted:#475569;
  --accent:#0ea5ff;
  --accent-ink:#083344;
  --ring:rgba(14,165,255,.25);
  --shadow:0 8px 24px rgba(2,8,23,.08);
}

*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";
  color:var(--ink);
  background:var(--bg);
  line-height:1.6;
}

/* ====== Hero ====== */
.hero{ position:relative; height: 320px; display:grid; place-items:center; overflow:hidden;}
.hero-bg{
  position:absolute; inset:0;
  background:url('images/neutrinos.jpeg') center/cover no-repeat;
  filter:contrast(1.05) saturate(1.05);
  transform:scale(1.02);
  opacity:0.5;
}
.hero-overlay{
  position:absolute; inset:0;
  background:linear-gradient(180deg,rgba(2,6,23,.55),rgba(2,6,23,.35) 40%, rgba(2,6,23,.2) 75%, transparent);
  mix-blend-multiply;
}
.hero-text{
  position:relative; text-align:center; color:#fff; padding:0 1rem;
}
.hero-text h1{font-size:clamp(1.6rem,3.2vw,2.4rem); margin:.25rem 0 .5rem}
.hero-text p{margin:0; opacity:.9}

/* ====== Navigation ====== */
.site-nav{
  position:sticky; top:0; z-index:20;
  background:#0b1328; color:#fff; border-bottom:1px solid rgba(255,255,255,.08);
  box-shadow:0 3px 12px rgba(2,8,23,.08);
}
.site-nav ul{margin:0; padding:.6rem .8rem; list-style:none; display:flex; flex-wrap:wrap; gap:.6rem 1rem; justify-content:center}
.site-nav a{
  color:#e5f4ff; text-decoration:none; padding:.35rem .6rem; border-radius:.5rem; transition:background .2s ease, color .2s ease;
}
.site-nav a:hover{ background:rgba(255,255,255,.08); }
.site-nav a.active{ background:#e0f2ff; color:#0b1328; font-weight:600; }

section{ scroll-margin-top: 84px; }

/* ====== Cards / Sections ====== */
.card{
  max-width: 980px; margin: 42px auto; padding: 28px;
  background:var(--card); border-radius:16px; box-shadow:var(--shadow);
}
.card h2{
  margin:0 0 24px; text-align:center; color:var(--accent-ink);
  letter-spacing:.2px;
  position:relative;
}
.card h2::after{
  content:""; display:block; width:64px; height:3px; margin:10px auto 0;
  background:linear-gradient(90deg, transparent, var(--accent), transparent);
  border-radius:2px;
}

/* ====== Intro text with image ====== */
.image-paragraph{ display:flex; gap:20px; align-items:flex-start; flex-wrap:wrap }
.image-paragraph p{ flex:1 1 460px; margin:0 }
.image-paragraph a{ color:var(--accent); text-decoration:none }
.image-paragraph a:hover{ text-decoration:underline }
.image-paragraph img{
  flex:0 0 260px; width:260px; height:260px; object-fit:cover;
  border-radius:50%; border:6px solid #fff; box-shadow:0 12px 28px rgba(2,8,23,.15);
}

/* ====== Timeline (Experience) ====== */
.timeline{ list-style:none; margin:0; padding:0 0 0 40px; position:relative }
.timeline::before{ content:""; position:absolute; left:14px; top:4px; bottom:4px; width:2px; background:linear-gradient(var(--accent),transparent) }
.timeline li{ position:relative; margin:0 0 18px; padding-left:2px }
.timeline li::before{
  content:""; position:absolute; left:-22px; top:.55rem; width:10px; height:10px; border-radius:50%;
  background:var(--accent); box-shadow:0 0 0 3px var(--ring);
}
.timeline p{ margin:.2rem 0 0 }

/* ====== Lists / items ====== */
.publication-item, .talk-item, .events-item, .award-item{ margin-bottom:16px }
.publication-item em{ color:var(--accent); display:block; margin-bottom:4px }
.talk-item em{ color:#0F385F; font-weight:700; display:block; margin-bottom:4px }
a{ color:var(--accent) }
a:hover{text-decoration:underline}

.social-logo{ width:30px; height:auto; margin:0 10px; vertical-align:middle }

/* ====== Collapsible sections ====== */
.collapsible .collapsible-inner{
  overflow:hidden;
  transition:max-height .6s ease;
  position:relative;
}
.collapsible:not(.expanded) .collapsible-inner::after{
  content:"";
  position:absolute; left:0; right:0; bottom:0; height:96px;
  background:linear-gradient(180deg, rgba(255,255,255,0), var(--card));
  pointer-events:none;
}
.toggle-section{
  display:none;
  margin: 10px auto 0; padding:.6rem 1rem;
  border-radius:999px; border:1px solid #cfe9ff; background:#eaf6ff;
  color:#0b1328; font-weight:600; cursor:pointer;
  transition: transform .12s ease, box-shadow .12s ease;
}
.toggle-section:hover{ transform:translateY(-1px); box-shadow:0 6px 18px rgba(2,8,23,.08) }
.toggle-section[aria-expanded="true"]{ background:#eef6ff; }

/* ====== Responsive YouTube embed ====== */
.video-container{
  position:relative;
  width:100%;
  max-width:840px;
  margin:12px auto 0;
  aspect-ratio:16/9;          /* modern browsers */
  background:#000;
  border-radius:12px;
  overflow:hidden;
  box-shadow:var(--shadow);
}
.video-container iframe{
  position:absolute; inset:0;
  width:100%; height:100%;
  border:0;
}

/* ====== Contact ====== */
.contact-list{ margin:0; padding-left:18px }
.contact-link{ color:var(--accent) }

/* ====== Footer ====== */
footer{
  background:#0b1328; color:#cfe2ff; text-align:center;
  padding:14px; margin-top:40px;
}

/* ====== Accessibility / Prefers reduced motion ====== */
@media (prefers-reduced-motion: reduce){
  html{ scroll-behavior:auto }
  .collapsible .collapsible-inner{ transition:none }
  .toggle-section{ transition:none }
}

/* ====== Responsive tweaks ====== */
@media (max-width: 820px){
  .hero{ height: 260px }
  .image-paragraph img{ margin:0 auto }
}