:root {
  /* Akzent / Marke */
  --accent: #ad1f1f;
  --accent-hover: #c42a2a;
  --accent-active: #961a1a;
  --accent-soft: rgba(173, 31, 31, 0.14);
  --accent-border: rgba(173, 31, 31, 0.55);
  --on-accent: #ffffff;

  /* Oberflächen / Neutral */
  --bg: #0b0b0d;
  --surface: #141417;
  --surface-2: #1c1c21;
  --surface-3: #26262d;
  --border: #2a2a31;
  --border-strong: #3a3a44;

  /* Text */
  --text: #ededf2;
  --text-muted: #a1a1ab;
  --text-faint: #6b6b76;

  /* Status */
  --success: #3fae6b;
  --success-soft: rgba(63, 174, 107, 0.14);
  --warning: #d8a23a;
  --warning-soft: rgba(216, 162, 58, 0.14);
  --danger: #d8453a;
  --danger-soft: rgba(216, 69, 58, 0.14);
  --danger-hover: #c23a30;

  /* Aliase auf die bestehenden Variablennamen (rückwärtskompatibel) */
  --bg-elev: var(--surface);
  --bg-elev-2: var(--surface-2);
  --hover-course: var(--surface-2);
  --hover-nested: var(--surface-3);
  --hover-lesson: var(--surface);
  --text-dim: var(--text-muted);
  --primary: var(--accent);
  --primary-hover: var(--accent-hover);

  --radius: 10px;
  --sidebar-w: 240px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica,
    Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 14px;
  line-height: 1.5;
}

a {
  color: var(--primary);
  text-decoration: none;
}

/* ----------------------------- Layout ----------------------------- */

.layout {
  display: flex;
  min-height: 100vh;
}

.sidebar {
  width: var(--sidebar-w);
  background: var(--bg-elev);
  border-right: 1px solid var(--border);
  padding: 24px 16px;
  position: fixed;
  inset: 0 auto 0 0;
  display: flex;
  flex-direction: column;
}

.sidebar .brand {
  font-size: 18px;
  font-weight: 700;
  padding: 0 8px 24px;
  color: var(--text);
}

.sidebar .brand span {
  color: var(--primary);
}

.sidebar .brand .brand-logo {
  display: block;
  max-width: 100%;
  max-height: 48px;
  width: auto;
  object-fit: contain;
}

.brand-placeholder {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 14px;
  border: 1px dashed var(--border);
  border-radius: 6px;
  color: var(--text-dim);
  font-size: 13px;
  font-weight: 500;
  text-align: center;
}

.nav {
  display: flex;
  flex-direction: column;
  gap: 4px;
  flex: 1;
}

.nav a {
  color: var(--text-dim);
  padding: 10px 12px;
  border-radius: var(--radius);
  font-weight: 500;
}

.nav a:hover {
  background: var(--bg-elev-2);
  color: var(--text);
}

.nav a.active {
  background: var(--bg-elev-2);
  color: var(--text);
}

.sidebar .foot {
  border-top: 1px solid var(--border);
  padding-top: 16px;
  color: var(--text-dim);
  font-size: 13px;
}

.content {
  margin-left: var(--sidebar-w);
  flex: 1;
  display: flex;
  flex-direction: column;
}

.topbar {
  height: 60px;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 28px;
  background: var(--bg-elev);
}

.topbar h1 {
  font-size: 17px;
  margin: 0;
}

.main {
  padding: 28px;
}

/* ----------------------------- Components ----------------------------- */

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-bottom: 28px;
}

.card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}

.card .label {
  color: var(--text-dim);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.card .value {
  font-size: 30px;
  font-weight: 700;
  margin-top: 6px;
}

.panel {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
}

.panel-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  border-bottom: 1px solid var(--border);
}

.panel-head h2 {
  font-size: 15px;
  margin: 0;
}

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

th,
td {
  text-align: left;
  padding: 12px 20px;
  border-bottom: 1px solid var(--border);
}

th {
  color: var(--text-dim);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

tr:last-child td {
  border-bottom: none;
}

.badge {
  display: inline-block;
  padding: 2px 8px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
}

.badge.green {
  background: var(--success-soft);
  color: var(--success);
}

.badge.gray {
  background: var(--bg-elev-2);
  color: var(--text-dim);
}

/* ----------------------------- Buttons ----------------------------- */

.btn {
  display: inline-block;
  padding: 9px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-elev-2);
  color: var(--text);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  text-align: center;
}

.btn:hover {
  border-color: var(--text-dim);
}

.btn-primary {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--on-accent);
}

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

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

.btn-danger:hover {
  background: var(--danger);
  color: var(--on-accent);
}

.btn-sm {
  padding: 5px 10px;
  font-size: 13px;
}

.btn-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 7px;
  line-height: 0;
}

.btn-icon svg {
  display: block;
}

.actions {
  display: flex;
  gap: 8px;
}

/* ----------------------------- Forms ----------------------------- */

.form {
  max-width: 560px;
}

.field {
  margin-bottom: 18px;
}

.field label {
  display: block;
  margin-bottom: 6px;
  color: var(--text-dim);
  font-weight: 600;
  font-size: 13px;
}

.field input,
.field select,
.field textarea {
  width: 100%;
  padding: 10px 12px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--text);
  font-size: 14px;
  font-family: inherit;
}

.field input:focus,
.field select:focus,
.field textarea:focus {
  outline: none;
  border-color: var(--primary);
}

.field input:disabled,
.field input[readonly] {
  background: var(--bg-elev-2);
  color: var(--text-dim);
  cursor: not-allowed;
  opacity: 0.7;
}

.field-row {
  display: flex;
  gap: 16px;
}

.field-row .field {
  flex: 1;
}

.checkbox {
  display: flex;
  align-items: center;
  gap: 8px;
}

.checkbox input {
  width: auto;
}

.alert {
  background: var(--danger-soft);
  border: 1px solid var(--danger);
  color: var(--danger);
  padding: 12px 16px;
  border-radius: var(--radius);
  margin-bottom: 20px;
}

/* ----------------------------- Login ----------------------------- */

.login-wrap {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
}

.login-card {
  width: 100%;
  max-width: 380px;
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px;
}

.login-card .brand {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 4px;
}

.login-card .brand span {
  color: var(--primary);
}

.login-card .brand .brand-logo {
  max-width: 100%;
  max-height: 56px;
  width: auto;
  object-fit: contain;
}

.login-card .sub {
  color: var(--text-dim);
  margin-bottom: 24px;
}

.page-actions {
  margin-bottom: 20px;
}

.muted {
  color: var(--text-dim);
}

/* ----------------------------- Tree (Accordion) ----------------------------- */

.tree {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.tree-item {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: background 0.15s ease;
}

/* Etwas hellerer Hintergrund nur für das Element, dessen eigene Kopfzeile gehovert wird */
.tree-item:has(> .tree-row:hover) {
  background: var(--hover-course);
}

.tree-item.nested:has(> .tree-row:hover) {
  background: var(--hover-nested);
}

.tree-item.nested {
  background: var(--bg-elev-2);
}

.tree-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 14px 16px;
}

.tree-row[data-toggle] {
  cursor: pointer;
  user-select: none;
}

.tree-row[data-toggle] .actions {
  cursor: default;
}

.tree-head {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 1;
  min-width: 0;
}

.tree-title {
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.chevron {
  display: inline-block;
  flex: none;
  width: 16px;
  color: var(--text-dim);
  transition: transform 0.25s ease;
}

.tree-item.open > .tree-row .chevron {
  transform: rotate(90deg);
}

.count {
  color: var(--text-dim);
  font-size: 13px;
  flex: none;
}

/* Smoothes Auf-/Zuklappen via grid-template-rows 0fr → 1fr */
.collapsible {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.3s ease;
}

.tree-item.open > .collapsible {
  grid-template-rows: 1fr;
}

.collapsible > .inner {
  overflow: hidden;
}

.tree-children {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 0 16px 14px 42px;
}

.empty-hint {
  padding: 0 16px 14px 42px;
  color: var(--text-dim);
}

.lesson-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 14px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: background 0.15s ease;
}

.lesson-row:hover {
  background: var(--hover-lesson);
}

.lesson-row .tree-head {
  cursor: default;
}

/* Aktions-Buttons erst beim Hovern (oder Fokus) der Zeile einblenden */
.tree-row .actions,
.lesson-row .actions {
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.15s ease;
}

.tree-row:hover .actions,
.tree-row:focus-within .actions,
.lesson-row:hover .actions,
.lesson-row:focus-within .actions {
  opacity: 1;
  pointer-events: auto;
}