:root{
  --bg: #ffffff;
  --surface: #f6f8fb;
  --text: #1f2937;
  --muted: #4b4b4b;
  --accent: #1d4ed8;
  --border: #e5e7eb;

  --radius: 14px;
  --shadow: 0 8px 24px rgba(17, 24, 39, 0.08);
}

*{ box-sizing: border-box; }
html, body{ height: 100%; }

body{
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", "Noto Sans JP", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
}

a{ color: var(--accent); text-decoration: none; }
a:hover{ text-decoration: underline; }
a.black{
  color: #1f2937
}

.container{
  width: min(100% - 32px, 980px);
  margin-inline: auto;
}

/* ---------------- Header / Nav ---------------- */
.site-header{
  position: sticky;
  top: 0;
  background: rgba(255,255,255,0.88);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
  z-index: 20;
}

.nav{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap: 12px;
  padding: 14px 0;
}

.brand{
  font-weight: 700;
  letter-spacing: 0.2px;
  color: var(--text);
}

.nav-right{
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

/* Language toggle */
.lang-toggle{
  display: inline-flex;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg);
  overflow: hidden;
}

.lang-btn{
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 8px 10px;
  font-size: 13px;
  color: var(--muted);
  text-decoration: none;
  min-width: 44px;
}

.lang-btn:hover{
  text-decoration: none;
  background: var(--surface);
  color: var(--text);
}

.lang-btn[aria-current]{
  color: white;
  background: var(--accent);
}

/* hamburger */
.hamburger{
  display: inline-flex;
  flex-direction: column;
  gap: 5px;
  padding: 10px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg);
  cursor: pointer;
}
.hamburger__bar{
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
}

/* menu - mobile dropdown */
.menu{
  position: absolute;
  left: 0;
  right: 0;
  top: 60px;
  margin: 0 auto;
  width: min(100% - 32px, 980px);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 10px;
  display: none;
  z-index: 30;
}
.menu a{
  display: block;
  padding: 10px 10px;
  color: var(--muted);
  border-radius: 10px;
}
.menu a:hover{
  background: var(--surface);
  color: var(--text);
  text-decoration: none;
}
.menu[data-open="true"]{ display: block; }

/* overlay */
.menu-overlay{
  position: fixed;
  inset: 0;
  background: rgba(17, 24, 39, 0.35);
  z-index: 25;
}

/* separator (mobile: horizontal, desktop: vertical) */
.menu-sep{
  display:block;
  height: 1px;
  background: var(--border);
  margin: 6px 6px;
}

/* active nav */
#site-menu a[aria-current="page"]{
  color: var(--text);
  font-weight: 700;
}
@media (max-width: 899px){
  #site-menu a[aria-current="page"]{
    background: var(--surface);
  }
}

/* prevent background scroll while menu open */
.no-scroll{ overflow: hidden; }

/* disabled link style (menu + toggle + others) */
a[aria-disabled="true"]{
  opacity: 0.45;
  pointer-events: none;
}

/* desktop nav */
@media (min-width: 900px){
  .hamburger{ display: none; }

  .menu{
    position: static;
    display: flex !important;
    gap: 16px;
    width: auto;
    background: transparent;
    border: none;
    box-shadow: none;
    padding: 0;
  }
  .menu a{
    display: inline;
    padding: 0;
    background: transparent;
  }
  .menu-overlay{ display: none; }

  .menu-sep{
    width: 1px;
    height: 18px;
    margin: 0 6px;
    display: inline-block;
    align-self: center;
  }
}

/* ---------------- Common Sections ---------------- */
.badge{
  display: inline-block;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  color: var(--muted);
  font-size: 13px;
}

h1{
  font-size: clamp(26px, 4vw, 40px);
  line-height: 1.2;
  margin: 14px 0 10px;
}
h2{
  margin: 0 0 10px;
  font-size: 23px;
}
h3{
  margin: 0 0 10px;
  font-size: 20px;
}
p{ margin: 0 0 12px; }

.lead{
  color: var(--muted);
  max-width: 70ch;
}

.section{ padding: 26px 0; }
.section-head{
  display:flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}
.kicker{ color: var(--muted); font-size: 14px; }

/* buttons */
.hero-links{
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
  margin-top: 14px;
}
.btn{
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 14px;
  border-radius: 10px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: white;
  font-weight: 600;
}
.btn.ghost{
  background: transparent;
  color: var(--accent);
}

/* cards */
.grid3{
  display: grid;
  gap: 14px;
  padding: 18px 0 10px;
  grid-template-columns: 1fr;
}
.card{
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 16px;
}
.card h3{
  margin: 0 0 8px;
  font-size: 18px;
}
.card p,li{ margin: 0; color: var(--muted); }

@media (min-width: 900px){
  .grid3{ grid-template-columns: repeat(3, 1fr); }
}

/* ---------------- Hero + Photo ---------------- */
.hero{ padding: 44px 0 10px; }
.hero-grid{
  display: grid;
  gap: 18px;
  grid-template-columns: 1fr;
  align-items: start;
}
@media (min-width: 900px){
  .hero-grid{ grid-template-columns: 1.5fr 1fr; }
}

.avatar{
  margin: 0;
  padding: 14px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}
.avatar img{
  width: 100%;
  display: block;
  border-radius: 12px;
  border: 1px solid var(--border);
  aspect-ratio: 4 / 5;
  object-fit: cover;
}
.avatar figcaption{
  margin-top: 10px;
  color: var(--muted);
  font-size: 14px;
}

/* ---------------- CV Timeline ---------------- */
.timeline{
  display: grid;
  gap: 10px;
  margin: 10px 0 0;
}
.tl-item{
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 12px;
  padding: 12px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}
.tl-date{
  color: var(--muted);
  font-feature-settings: "tnum";
  font-variant-numeric: tabular-nums;
}
.tl-body{ margin: 0; }
@media (max-width: 520px){
  .tl-item{ grid-template-columns: 1fr; }
}

/* ---------------- Research list (citation-like) ---------------- */
.pub-list{
  list-style: none;
  padding: 0;
  margin: 12px 0 0;
  display: grid;
  gap: 10px;
}
.pub{
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px 14px 12px;
}
.pub-title{
  margin: 0 0 6px;
  font-weight: 700;
  line-height: 1.4;
}
.pub-meta{
  margin: 0;
  color: var(--muted);
  font-size: 14px;
}
.pub-links{
  margin-top: 10px;
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}
.pill{
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 10px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: #fff;
  color: var(--text);
  font-size: 13px;
}
.pill:hover{
  text-decoration: none;
  border-color: #cbd5e1;
}
.pub em{ font-style: normal; font-weight: 700; color: var(--text); }

/* ---------------- Footer ---------------- */
.site-footer{
  border-top: 1px solid var(--border);
  margin-top: 30px;
  padding: 18px 0;
  color: var(--muted);
}
.footer-inner{
  display:flex;
  align-items:center;
  justify-content:space-between;
  gap: 12px;
  flex-wrap: wrap;
}
.footer-links{
  display:flex;
  gap: 12px;
}