:root {
  --bg: #f7f9fc;
  --card: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --primary: #2563eb;
  --primary-600: #1d4ed8;
  --accent: #10b981;
  --danger: #ef4444;
  --warning: #f59e0b;
  --border: #e2e8f0;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--text);
  background: var(--bg);
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Helvetica,
    Arial, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", sans-serif;
}

header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 12px 16px;
  background: var(--card);
  border-bottom: 1px solid var(--border);
}

header .brand {
  display: flex;
  align-items: center;
  gap: 10px;
}

header .brand h1 {
  font-size: 18px;
  margin: 0;
}

.layout {
  display: grid;
  grid-template-columns: 240px 1fr;
  gap: 16px;
  padding: 16px;
}

nav {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px;
  height: fit-content;
}

nav h3 {
  margin: 6px 0 10px;
  font-size: 14px;
  color: var(--muted);
}

nav button,
nav a {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 12px;
  margin: 6px 0;
  border: 1px solid var(--border);
  background: #fff;
  color: var(--text);
  border-radius: 8px;
  cursor: pointer;
}

nav button.active {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

main {
  min-height: 60vh;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px;
  margin-bottom: 16px;
}

.row {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.row > * {
  flex: 1;
  min-width: 240px;
}

input[type="text"],
input[type="number"],
input[type="time"],
input[type="date"],
select,
textarea {
  width: 100%;
  padding: 8px 10px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 14px;
}

textarea {
  min-height: 120px;
}

.btn {
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  cursor: pointer;
}

.btn.primary {
  background: var(--primary);
  color: #fff;
  border-color: var(--primary);
}

.btn.success {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn.warn {
  background: var(--warning);
  border-color: var(--warning);
  color: #fff;
}

.btn.danger {
  background: var(--danger);
  border-color: var(--danger);
  color: #fff;
}

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

th,
td {
  border: 1px solid var(--border);
  padding: 8px;
  vertical-align: top;
  text-align: left;
}

th {
  background: #f8fafc;
}

.group-box {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.group {
  flex: 1;
  min-width: 240px;
  background: #eef6ff;
  padding: 10px;
  border-radius: 10px;
}

.student {
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 6px 8px;
  margin: 6px 0;
  cursor: grab;
}

.drag-over {
  outline: 2px dashed var(--primary);
}

.toolbar {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  align-items: center;
  margin-bottom: 10px;
}

.muted {
  color: var(--muted);
  font-size: 12px;
}

.chip {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 2px 8px;
  border: 1px solid var(--border);
  border-radius: 999px;
  font-size: 12px;
  background: #fff;
}

.status-ok {
  color: var(--accent);
}

.status-warn {
  color: var(--warning);
}

.status-bad {
  color: var(--danger);
}

.hidden {
  display: none !important;
}

.grid {
  display: grid;
  gap: 12px;
}

.grid.cols-2 {
  grid-template-columns: repeat(2, 1fr);
}

.grid.cols-3 {
  grid-template-columns: repeat(3, 1fr);
}

.right {
  text-align: right;
}

@media (max-width: 900px) {
  .layout {
    grid-template-columns: 1fr;
  }
  nav {
    order: 2;
  }
}