:root{
  --bg:#f5f7fb;
  --card:#ffffff;
  --line:#e6eaf2;
  --text:#1f2937;
  --muted:#6b7280;
  --primary:#3b82f6;
}
*{box-sizing:border-box}
html,body{overflow-x:hidden}
body{
  margin:0;
  font-family:Inter,-apple-system,BlinkMacSystemFont,"Segoe UI","PingFang SC","Microsoft YaHei",Arial,sans-serif;
  color:var(--text);
  background:linear-gradient(180deg,#f8faff 0%,var(--bg) 180px);
}

header,main{
  width:min(1200px,calc(100vw - 24px));
  margin:0 auto;
}

header{
  margin-top:12px;
  margin-bottom:10px;
  padding:14px 16px;
  background:rgba(255,255,255,.9);
  border:1px solid var(--line);
  border-radius:14px;
  backdrop-filter: blur(6px);
  display:flex;
  gap:12px;
  align-items:center;
  flex-wrap:wrap;
}

h1{
  margin:0 6px 0 0;
  font-size:18px;
  letter-spacing:.2px;
}

label{font-size:13px;color:var(--muted);display:flex;gap:8px;align-items:center}
select{
  border:1px solid #d7ddea;
  background:#fff;
  border-radius:10px;
  padding:6px 10px;
}

.year-quick{display:flex;gap:8px;flex-wrap:wrap}
.year-quick button{
  border:1px solid #d7ddea;
  background:#fff;
  color:#374151;
  border-radius:999px;
  padding:4px 11px;
  cursor:pointer;
}
.year-quick .active{
  background:#111827;
  border-color:#111827;
  color:#fff;
}

main{
  display:grid;
  grid-template-columns:300px minmax(0,1fr);
  gap:12px;
  padding:0 0 14px;
}

aside,section{
  background:var(--card);
  border:1px solid var(--line);
  border-radius:14px;
  padding:12px;
  box-shadow:0 4px 18px rgba(25,35,55,.04);
}

aside h3{margin:4px 0 10px;font-size:16px}

aside{
  position:sticky;
  top:12px;
  align-self:start;
  max-height:calc(100vh - 24px);
  display:flex;
  flex-direction:column;
}

#questionList{list-style:none;padding:0;margin:0;overflow:auto;flex:1;min-height:0}
#questionList li{padding:7px 9px;border-radius:8px}
#questionList .group{
  font-weight:700;
  color:#374151;
  margin-top:8px;
  background:#f8fafc;
  border:1px solid #edf1f7;
}
#questionList .child{margin-left:10px;cursor:pointer}
#questionList .child:hover{background:#f1f5ff}
#questionList .child.active{background:#e9f1ff;color:#1d4ed8;font-weight:600}

#qTitle{margin:2px 0 8px;font-size:20px;line-height:1.35}
.tagbar{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:10px}
.tag{background:#eef2ff;color:#3730a3;border:1px solid #c7d2fe;border-radius:999px;padding:2px 8px;font-size:12px}

.tabs{display:flex;gap:7px;margin:10px 0 12px;flex-wrap:wrap}
.tabs button{
  border:1px solid #d7ddea;
  background:#fff;
  border-radius:999px;
  padding:5px 12px;
  cursor:pointer;
}
.tabs .active{background:var(--primary);color:#fff;border-color:var(--primary)}

#panel{
  line-height:1.8;
  font-size:15px;
  white-space:normal;
  max-width:900px;
}

.mobile-nav{display:none !important}
.mobile-backdrop{display:none}

@media (max-width: 900px){
  header,main{width:min(100vw - 16px,1200px)}
  header{margin-top:8px;padding:10px 12px;border-radius:12px}
  main{grid-template-columns:1fr;gap:10px;padding-bottom:70px}
  section{order:1}

  #sidebar{
    position:fixed;
    left:8px;
    right:8px;
    bottom:76px;
    top:72px;
    z-index:50;
    max-height:none;
    transform:translate3d(0,110%,0);
    transition:transform .22s ease;
    will-change:transform;
    background:#fff;
    pointer-events:none;
  }
  #sidebar.open{
    transform:translate3d(0,0,0);
    pointer-events:auto;
  }

  .mobile-backdrop{
    display:block;
    position:fixed;
    inset:0;
    background:rgba(15,23,42,.28);
    opacity:0;
    pointer-events:none;
    transition:opacity .2s ease;
    z-index:45;
  }
  body.sidebar-open .mobile-backdrop{
    opacity:1;
    pointer-events:auto;
  }
  body.sidebar-open{overflow:hidden}

  #questionList{max-height:calc(100vh - 170px)}
  #qTitle{font-size:18px}
  #panel{font-size:14px;max-width:100%}

  .mobile-nav{
    display:grid !important;
    grid-template-columns:1fr 1fr 1fr;
    gap:10px;
    position:fixed;
    left:0;
    right:0;
    bottom:0;
    z-index:60;
    width:100vw;
    transform:translateZ(0);
    -webkit-transform:translateZ(0);
    padding:10px 12px calc(10px + env(safe-area-inset-bottom));
    background:rgba(255,255,255,.92);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-top:1px solid var(--line);
    box-shadow:0 -4px 16px rgba(0,0,0,.06);
  }
  .mobile-nav button{
    border:1px solid #dbe2ef;
    background:#fff;
    border-radius:999px;
    padding:10px 12px;
    font-size:14px;
    font-weight:600;
    color:#334155;
  }
  .mobile-nav button:active{transform:scale(.98)}
}