:root{
  --bg:#f6f7fb;
  --paper:#ffffff;
  --ink:#172033;
  --muted:#667085;
  --line:#d8dce8;
  --primary:#2563eb;
  --primary-dark:#1d4ed8;
  --success:#16a34a;
  --danger:#dc2626;
  --warning:#f59e0b;
  --shadow:0 12px 35px rgba(15,23,42,.12);
  --radius:18px;
}

*{box-sizing:border-box}
html,body{margin:0;min-height:100%;font-family:system-ui,-apple-system,"Segoe UI",Tahoma,Arial,sans-serif;background:var(--bg);color:var(--ink)}
body{height:100dvh;overflow:hidden}
button,input{font-family:inherit}
.hidden{display:none!important}
#app{height:100dvh;display:flex;flex-direction:column;min-height:0}

.topbar{flex:0 0 auto;min-height:86px;padding:16px 24px;background:linear-gradient(135deg,#12203a,#1e3a8a);color:#fff;display:flex;justify-content:space-between;gap:16px;align-items:center;box-shadow:var(--shadow);z-index:5}
.topbar h1{margin:0 0 6px;font-size:26px}
.topbar p{margin:0;color:#dbeafe;max-width:850px;line-height:1.7}
.top-actions{display:flex;gap:10px;flex-wrap:wrap}

.btn{border:1px solid var(--line);background:#fff;color:var(--ink);border-radius:12px;padding:10px 14px;cursor:pointer;font-weight:700;transition:.15s;box-shadow:0 2px 8px rgba(15,23,42,.06);white-space:nowrap}
.btn:hover{transform:translateY(-1px);box-shadow:0 6px 18px rgba(15,23,42,.12)}
.btn:disabled{opacity:.5;cursor:not-allowed;transform:none}
.btn.primary{background:var(--primary);border-color:var(--primary);color:#fff}
.btn.primary:hover{background:var(--primary-dark)}
.btn.success{background:var(--success);border-color:var(--success);color:#fff}
.btn.warning{background:var(--warning);border-color:var(--warning);color:#fff}
.btn.danger{background:var(--danger);border-color:var(--danger);color:#fff}
.btn.ghost{background:rgba(255,255,255,.14);color:#fff;border-color:rgba(255,255,255,.25)}

.import-panel{flex:1;min-height:0;display:grid;place-items:center;padding:22px;overflow:auto}
.import-card{width:min(620px,100%);background:var(--paper);border-radius:26px;padding:38px;text-align:center;box-shadow:var(--shadow);border:1px solid var(--line)}
.upload-icon{font-size:58px}
.import-card h2{margin:10px 0}
.import-card p{color:var(--muted);line-height:1.8}
.import-card .btn{margin:6px}
.import-card .ghost{background:#f1f5f9;color:var(--ink)}

.workspace-shell{flex:1;min-height:0;display:grid;grid-template-columns:320px minmax(0,1fr);overflow:hidden}
.sidebar{overflow:auto;padding:16px;background:#edf1f7;border-left:1px solid var(--line);min-height:0;overscroll-behavior:contain}
.panel{background:var(--paper);border:1px solid var(--line);border-radius:var(--radius);padding:14px;margin-bottom:14px;box-shadow:0 6px 18px rgba(15,23,42,.05)}
.panel h3{margin:0 0 12px}
.stats{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}
.stats div{background:#f8fafc;border:1px solid var(--line);border-radius:14px;padding:10px;text-align:center}
.stats span{display:block;font-size:24px;font-weight:900;color:var(--primary)}
.stats small{color:var(--muted)}
.control-grid{display:grid;gap:8px}
.text-input{width:100%;border:1px solid var(--line);border-radius:12px;padding:11px 12px;font-size:15px;outline:none;background:#fff}
.text-input:focus{border-color:var(--primary);box-shadow:0 0 0 3px rgba(37,99,235,.12)}
.inline-form{display:grid;grid-template-columns:1fr auto;gap:8px}
.small-note{color:var(--muted);line-height:1.7}
.small-note p{margin:6px 0 0}
.search-results{margin-top:10px;display:grid;gap:6px;max-height:210px;overflow:auto}
.search-item{border:1px solid var(--line);border-radius:12px;padding:8px;background:#fff;cursor:pointer}
.search-item:hover{border-color:var(--primary)}
.search-item small{display:block;color:var(--muted);line-height:1.6}

.workspace-wrap{display:flex;flex-direction:column;min-width:0;min-height:0;overflow:hidden}
.workspace-toolbar{flex:0 0 auto;min-height:46px;display:flex;justify-content:space-between;align-items:center;gap:12px;padding:8px 14px;border-bottom:1px solid var(--line);background:#fff;z-index:3}
.legend{display:flex;gap:16px;color:var(--muted);font-size:14px;flex-wrap:wrap}
.dot{display:inline-block;width:10px;height:10px;border-radius:50%;margin-left:5px}
.dot.unchanged{background:#94a3b8}
.dot.moved{background:var(--warning)}
.file-name{color:var(--muted);font-size:14px;direction:ltr;max-width:45%;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}

.workspace{position:relative;flex:1;min-height:0;overflow:auto;background:radial-gradient(circle at 1px 1px,#d7ddea 1px,transparent 0);background-size:24px 24px;direction:ltr;overscroll-behavior:contain}
.rings-layer{position:relative;width:1400px;height:900px;min-width:100%;min-height:100%;direction:rtl}
.arrow-layer{position:absolute;top:0;left:0;width:1400px;height:900px;pointer-events:none;color:#ef7b00;z-index:1;overflow:visible;direction:ltr}
.arrow-layer path{fill:none;stroke:currentColor;stroke-width:2.6;stroke-linecap:round;stroke-dasharray:8 6;marker-end:url(#arrowHead);opacity:.82;vector-effect:non-scaling-stroke}

.ring-card{position:absolute;width:280px;min-height:160px;background:rgba(255,255,255,.97);border:1px solid var(--line);border-radius:18px;box-shadow:var(--shadow);z-index:2;overflow:hidden;direction:rtl;touch-action:none}
.ring-card.dragging{opacity:.92;box-shadow:0 18px 45px rgba(37,99,235,.25);border-color:var(--primary);z-index:4}
.ring-header{display:flex;align-items:center;justify-content:space-between;gap:8px;background:linear-gradient(135deg,#f8fafc,#eef2ff);border-bottom:1px solid var(--line);padding:12px 14px;cursor:move;user-select:none;touch-action:none}
.ring-title{font-size:16px;margin:0;line-height:1.5}
.ring-count{font-size:12px;color:var(--muted)}
.ring-collapse{border:0;background:#e2e8f0;border-radius:10px;width:30px;height:30px;cursor:pointer;font-weight:900;flex:0 0 auto}
.student-list{min-height:95px;padding:10px;display:grid;align-content:start;gap:7px}
.ring-card.collapsed .student-list{display:none}
.ring-card.collapsed{min-height:auto}
.ring-card.drop-target{outline:3px solid rgba(37,99,235,.28);outline-offset:3px}

.student-chip{border:1px solid #d7deea;background:#fff;border-radius:13px;padding:9px 10px;cursor:grab;box-shadow:0 2px 7px rgba(15,23,42,.05);display:flex;justify-content:space-between;gap:8px;align-items:center;touch-action:auto}
.student-chip:hover{border-color:var(--primary)}
.student-chip:active{cursor:grabbing}
.student-chip.moved{background:#fff7ed;border-color:#fdba74}
.student-name{font-weight:700;line-height:1.5}
.student-origin{font-size:11px;color:#a16207;white-space:nowrap}
.student-chip.highlight{outline:3px solid rgba(37,99,235,.22);background:#eff6ff}

.modal{border:0;border-radius:20px;box-shadow:var(--shadow);max-width:620px;padding:24px;line-height:1.9}
.modal::backdrop{background:rgba(15,23,42,.45)}
.modal h2{margin-top:0}
.modal .btn{margin-top:10px}

@media (max-width:900px){
  body{overflow:hidden}
  .topbar{align-items:flex-start;flex-direction:column;padding:14px 16px}
  .topbar h1{font-size:22px}
  .topbar p{font-size:14px}
  .workspace-shell{grid-template-columns:1fr;grid-template-rows:minmax(210px,34dvh) minmax(0,1fr)}
  .sidebar{height:auto;border-left:0;border-bottom:1px solid var(--line);padding:10px;display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}
  .panel{margin:0}
  .workspace-toolbar{align-items:flex-start;flex-direction:column;gap:6px}
  .file-name{max-width:100%}
}

@media (max-width:560px){
  .top-actions{width:100%}
  .top-actions .btn{flex:1}
  .sidebar{grid-template-columns:1fr}
  .workspace-shell{grid-template-rows:minmax(230px,38dvh) minmax(0,1fr)}
  .ring-card{width:260px}
}

@media print{
  body{height:auto;overflow:visible}
  .topbar,.sidebar,.workspace-toolbar{display:none}
  .workspace-shell{display:block;height:auto}
  .workspace{overflow:visible}
  .ring-card{box-shadow:none}
}