:root {
  --bg: #0b0f14;
  --card: #121821;
  --muted: #273142;
  --text: #e8f0ff;
  --accent: #4da3ff;
  --accent-2: #00d2a8;
  --danger: #ff5d5d;
  --border: #2a3647;
  --success: #00d2a8;
  --warning: #ffc107;
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: linear-gradient(180deg, #0b0f14, #151b26 40%, #0b0f14);
  color: var(--text);
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px 24px;
  border-bottom: 1px solid var(--border);
  background: rgba(18,24,33,0.95);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 100;
}

.topbar h1 {
  font-size: 20px;
  letter-spacing: 1px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.topbar .actions {
  display: flex;
  gap: 10px;
  align-items: center;
}

button {
  padding: 8px 16px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: #1a2535;
  color: var(--text);
  cursor: pointer;
  font-size: 14px;
  transition: all 0.2s;
}

button:hover {
  border-color: var(--accent);
  background: #1e2d42;
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.btn-link {
  padding: 8px 16px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: #1a2535;
  color: var(--text);
  text-decoration: none;
  font-size: 14px;
  transition: all 0.2s;
}

.btn-link:hover {
  border-color: var(--accent);
  background: #1e2d42;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent), #3d8bff);
  border-color: var(--accent);
  color: white;
  font-weight: 600;
}

.btn-primary:hover {
  background: linear-gradient(135deg, #5db3ff, #4d93ff);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(77, 163, 255, 0.3);
}

.btn-secondary {
  background: #1a1f29;
}

.btn-danger {
  background: #2a1220;
  border-color: #3a1a27;
  color: #ffb3c2;
}

.btn-danger:hover {
  background: #3a1a27;
  border-color: #ff5d5d;
}

.main-content {
  padding: 24px;
  max-width: 1400px;
  margin: 0 auto;
}

.stats-bar {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}

.stat-item {
  background: rgba(18,24,33,0.6);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
  text-align: center;
}

.stat-label {
  display: block;
  font-size: 14px;
  color: #8a9bb5;
  margin-bottom: 8px;
}

.stat-value {
  display: block;
  font-size: 32px;
  font-weight: 700;
  color: var(--accent);
}

.filter-bar {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.search-input {
  flex: 1;
  min-width: 250px;
  padding: 10px 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card);
  color: var(--text);
  font-size: 14px;
  outline: none;
}

.search-input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(77, 163, 255, 0.1);
}

.filter-select {
  padding: 10px 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card);
  color: var(--text);
  font-size: 14px;
  outline: none;
  cursor: pointer;
  min-width: 150px;
}

.filter-select:focus {
  border-color: var(--accent);
}

.table-container {
  background: rgba(18,24,33,0.6);
  border: 1px solid var(--border);
  border-radius: 12px;
  overflow: hidden;
}

.student-table {
  width: 100%;
  border-collapse: collapse;
}

.student-table thead {
  background: rgba(39, 49, 66, 0.5);
}

.student-table th {
  padding: 14px 12px;
  text-align: left;
  font-weight: 600;
  font-size: 13px;
  color: #8a9bb5;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  border-bottom: 1px solid var(--border);
}

.student-table td {
  padding: 12px;
  border-bottom: 1px solid var(--border);
  font-size: 14px;
}

.student-table tbody tr {
  transition: background 0.2s;
}

.student-table tbody tr:hover {
  background: rgba(77, 163, 255, 0.05);
}

.student-table tbody tr:last-child td {
  border-bottom: none;
}

.loading {
  text-align: center;
  padding: 40px !important;
  color: #8a9bb5;
}

.action-btns {
  display: flex;
  gap: 8px;
}

.action-btns button {
  padding: 6px 12px;
  font-size: 12px;
}

.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0, 0, 0, 0.7);
  z-index: 1000;
  align-items: center;
  justify-content: center;
  -webkit-backdrop-filter: blur(4px);
  backdrop-filter: blur(4px);
}

.modal.active {
  display: flex;
}

.modal-content {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  width: 90%;
  max-width: 600px;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.5);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 24px;
  border-bottom: 1px solid var(--border);
}

.modal-header h2 {
  font-size: 18px;
  font-weight: 600;
}

.modal-close {
  background: none;
  border: none;
  color: #8a9bb5;
  font-size: 28px;
  cursor: pointer;
  padding: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
}

.modal-close:hover {
  background: rgba(255, 93, 93, 0.1);
  color: var(--danger);
}

.student-form {
  padding: 24px;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 16px;
}

.form-group {
  display: flex;
  flex-direction: column;
}

.form-group label {
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 6px;
  color: #cdd8f3;
}

.required {
  color: var(--danger);
}

.form-group input {
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 14px;
  outline: none;
  transition: all 0.2s;
}

.form-group input:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(77, 163, 255, 0.1);
}

.form-actions {
  display: flex;
  gap: 12px;
  margin-top: 24px;
  padding-top: 20px;
  border-top: 1px solid var(--border);
}

.import-content {
  padding: 24px;
}

.import-info {
  background: rgba(39, 49, 66, 0.3);
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 20px;
}

.import-info h3 {
  font-size: 14px;
  margin-bottom: 10px;
  color: var(--accent);
}

.import-info p {
  font-size: 13px;
  color: #8a9bb5;
  margin-bottom: 10px;
}

.import-info pre {
  background: var(--bg);
  padding: 12px;
  border-radius: 6px;
  font-size: 12px;
  overflow-x: auto;
  color: var(--accent-2);
}

.import-actions {
  display: flex;
  gap: 12px;
}

.import-status {
  margin-top: 16px;
  padding: 12px;
  border-radius: 8px;
  font-size: 14px;
}

.import-status.success {
  background: rgba(0, 210, 168, 0.1);
  border: 1px solid var(--success);
  color: var(--success);
}

.import-status.error {
  background: rgba(255, 93, 93, 0.1);
  border: 1px solid var(--danger);
  color: var(--danger);
}

@media (max-width: 768px) {
  .topbar {
    flex-direction: column;
    gap: 12px;
    padding: 12px;
  }
  
  .topbar .actions {
    flex-wrap: wrap;
    justify-content: center;
  }
  
  .form-row {
    grid-template-columns: 1fr;
  }
  
  .filter-bar {
    flex-direction: column;
  }
  
  .student-table {
    font-size: 12px;
  }
  
  .student-table th,
  .student-table td {
    padding: 8px 6px;
  }
}