:root{
  --bg:#f5f6f8;
  --card:#ffffff;
  --text:#1f2430;
  --muted:#6b7280;
  --border:#e5e7eb;
  --primary:#2f5fd7;
  --primary-dark:#2447ab;
  --success:#1a9c5c;
  --danger:#d0342c;
  --warn:#b8790a;
  --radius:10px;
}
*{box-sizing:border-box}
body{
  margin:0;
  font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Helvetica,Arial,sans-serif;
  background:var(--bg);
  color:var(--text);
}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}

.topbar{background:var(--card);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:10}
.topbar-inner{max-width:1000px;margin:0 auto;padding:14px 20px;display:flex;justify-content:space-between;align-items:center}
.brand{font-weight:700;font-size:18px;color:var(--text)}
.topnav{display:flex;align-items:center;gap:16px;font-size:14px}
.user-chip{color:var(--muted)}
.role-badge{padding:2px 8px;border-radius:999px;font-size:12px;font-weight:600;background:#eef1fb;color:var(--primary-dark)}
.role-admin{background:#fde8e8;color:#b91c1c}
.role-teacher{background:#e8f3fd;color:#1d4ed8}
.role-student{background:#e8fbf1;color:#0f7a44}

.container{max-width:1000px;margin:0 auto;padding:28px 20px 60px}

.card{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);padding:22px;margin-bottom:20px}
.card h2, .card h3{margin-top:0}

.alert{padding:12px 16px;border-radius:var(--radius);margin-bottom:18px;font-size:14px}
.alert-success{background:#e8fbf1;color:#0f7a44;border:1px solid #b9ecd2}
.alert-danger{background:#fde8e8;color:#b91c1c;border:1px solid #f7c2c2}
.alert-info{background:#e8f3fd;color:#1d4ed8;border:1px solid #bcd9f7}

label{display:block;font-size:13px;font-weight:600;margin-bottom:6px;color:var(--muted)}
input[type=text], input[type=email], input[type=password], input[type=search], select{
  width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:8px;font-size:14px;margin-bottom:14px;background:#fff;color:var(--text)
}
input:focus, select:focus{outline:2px solid var(--primary);outline-offset:1px}

.btn{
  display:inline-block;padding:9px 16px;border-radius:8px;border:1px solid var(--primary);
  background:var(--primary);color:#fff;font-size:14px;font-weight:600;cursor:pointer;
}
.btn:hover{background:var(--primary-dark);text-decoration:none}
.btn-outline{background:#fff;color:var(--primary)}
.btn-danger{background:#fff;color:var(--danger);border-color:var(--danger)}
.btn-danger:hover{background:var(--danger);color:#fff}
.btn-sm{padding:5px 10px;font-size:12.5px}

table{width:100%;border-collapse:collapse;font-size:14px}
th, td{text-align:left;padding:10px 8px;border-bottom:1px solid var(--border)}
th{color:var(--muted);font-weight:600;font-size:12.5px;text-transform:uppercase;letter-spacing:.03em}
tr:last-child td{border-bottom:none}

.grid{display:grid;gap:16px}
.grid-3{grid-template-columns:repeat(auto-fit,minmax(180px,1fr))}

.stat{background:var(--card);border:1px solid var(--border);border-radius:var(--radius);padding:18px;text-align:center}
.stat .num{font-size:28px;font-weight:700;color:var(--primary)}
.stat .label{color:var(--muted);font-size:13px;margin-top:4px}

.group-list a.group-link{
  display:block;background:var(--card);border:1px solid var(--border);border-radius:var(--radius);
  padding:16px 18px;margin-bottom:10px;color:var(--text);font-weight:600;
}
.group-list a.group-link:hover{border-color:var(--primary);text-decoration:none}
.group-list .meta{color:var(--muted);font-weight:400;font-size:13px;margin-top:4px}

.file-row{display:flex;align-items:center;justify-content:space-between;padding:12px 0;border-bottom:1px solid var(--border)}
.file-row:last-child{border-bottom:none}
.file-info{display:flex;align-items:center;gap:12px}
.file-icon{font-size:22px}
.file-name{font-weight:600}
.file-meta{color:var(--muted);font-size:12.5px}
.file-actions{display:flex;gap:8px;align-items:center}

.dropzone{
  border:2px dashed var(--border);border-radius:var(--radius);padding:30px;text-align:center;
  color:var(--muted);margin-bottom:16px;background:#fafbfc;transition:.15s;
}
.dropzone.drag{border-color:var(--primary);background:#eef3fd;color:var(--primary-dark)}

.upload-item{background:#fafbfc;border:1px solid var(--border);border-radius:8px;padding:10px 14px;margin-bottom:8px;font-size:13.5px}
.upload-item .bar-bg{background:#e5e7eb;border-radius:99px;height:6px;margin-top:6px;overflow:hidden}
.upload-item .bar-fg{background:var(--primary);height:100%;width:0%;transition:width .2s}
.upload-item.done .bar-fg{background:var(--success)}
.upload-item.error{color:var(--danger)}

.footer{text-align:center;color:var(--muted);font-size:12.5px;padding:20px}

.checkbox-list{display:grid;grid-template-columns:repeat(auto-fill,minmax(160px,1fr));gap:6px;margin-bottom:14px}
.checkbox-list label{display:flex;align-items:center;gap:6px;font-weight:400;font-size:14px;color:var(--text)}
.checkbox-list input{width:auto;margin:0}

.form-narrow{max-width:420px}
.top-actions{display:flex;justify-content:space-between;align-items:center;margin-bottom:16px;flex-wrap:wrap;gap:10px}
.badge{display:inline-block;padding:2px 8px;border-radius:999px;font-size:12px;background:#eef1fb;color:var(--primary-dark)}
.empty{color:var(--muted);font-style:italic;padding:16px 0}