* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f6f8fb;
  color: #1d1f25;
}

header {
  padding: 24px 16px 16px;
  text-align: center;
  background: #1c3d6a;
  color: white;
}

header h1 {
  margin: 0;
  font-size: 1.8rem;
}

header .subtitle {
  margin: 8px 0 0;
  opacity: 0.85;
}

main {
  max-width: 960px;
  margin: 24px auto 48px;
  padding: 0 16px;
}

.card {
  background: white;
  border-radius: 10px;
  padding: 16px;
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.07);
  margin-bottom: 24px;
}

.auth-tabs {
  display: flex;
  gap: 10px;
  margin-bottom: 18px;
}

.auth-tab {
  flex: 1;
  padding: 10px 14px;
  border: 1px solid #c8cbd2;
  border-radius: 10px;
  background: white;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.15s ease, border-color 0.15s ease;
}

.auth-tab:hover {
  background: #f4f6fb;
}

.auth-tab.active {
  border-color: #2f62d1;
  background: rgba(47, 98, 209, 0.1);
}

.auth-panel {
  padding-top: 8px;
}

.row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 12px;
  margin-top: 16px;
}

#teacher-management h3 {
  margin: 0;
  font-size: 1.05rem;
}

.row label {
  font-weight: 600;
  display: block;
}

.row input,
.row select,
.row textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid #c8cbd2;
  border-radius: 8px;
  font-size: 1rem;
}

.row button {
  padding: 10px 16px;
  border-radius: 8px;
  border: 1px solid #2f62d1;
  background: #2f62d1;
  color: white;
  font-weight: 600;
  cursor: pointer;
}

.row button:hover {
  background: #2a55b8;
}

.primary {
  background: #0b9b77;
  border-color: #0b9b77;
}

.primary:hover {
  background: #088a6b;
}

.hidden {
  display: none !important;
}

.table-wrapper {
  overflow-x: auto;
  margin-top: 12px;
}

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 8px;
}

table th,
table td {
  text-align: left;
  padding: 10px 12px;
  border-bottom: 1px solid #eef0f5;
}

table th {
  background: #f3f6ff;
  font-weight: 700;
}

button.small {
  padding: 6px 10px;
  font-size: 0.95rem;
}

footer {
  text-align: center;
  padding: 16px 12px 24px;
  font-size: 0.9rem;
  color: #55606d;
}

@media (min-width: 720px) {
  .row {
    grid-template-columns: repeat(2, 1fr);
  }
}