:root {
  --bg: #f6f7fb;
  --panel: #ffffff;
  --ink: #172033;
  --muted: #667085;
  --line: #d9deea;
  --brand: #2764e8;
  --brand-strong: #1744a4;
  --accent: #0f9f8f;
  --danger: #c23b4b;
  --warning: #b7791f;
  --shadow: 0 14px 32px rgba(25, 38, 66, .10);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--ink);
  display: grid;
  grid-template-columns: var(--sidebar-width, 280px) minmax(0, 1fr);
  min-height: 100vh;
}

.sidebar {
  background: #111827;
  color: #f9fafb;
  padding: 28px 22px;
  display: flex;
  flex-direction: column;
  gap: 28px;
  position: sticky;
  top: 0;
  height: 100vh;
  min-width: 72px;
  width: var(--sidebar-width, 280px);
  transition: width .16s ease, padding .16s ease;
}

.sidebar.collapsed {
  padding: 22px 14px;
}

body.sidebar-collapsed {
  grid-template-columns: 72px minmax(0, 1fr);
  --sidebar-width: 72px;
}

.brand, nav a {
  color: inherit;
  text-decoration: none;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 0;
}

.brand-mark {
  width: 44px;
  height: 44px;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: var(--brand);
  font-weight: 800;
}

.brand small, .account span {
  display: block;
  color: #b9c0cf;
  margin-top: 3px;
}

.sidebar-text {
  min-width: 0;
}

.sidebar-toggle {
  position: absolute;
  top: 14px;
  right: 12px;
  width: 30px;
  height: 30px;
  border: 1px solid #334155;
  border-radius: 8px;
  background: #1f2937;
  color: #f8fafc;
  cursor: pointer;
  font-size: 1.25rem;
  line-height: 1;
}

.sidebar-resizer {
  position: absolute;
  top: 0;
  right: -4px;
  width: 8px;
  height: 100%;
  cursor: col-resize;
}

.sidebar-resizer:hover,
body.sidebar-resizing .sidebar-resizer {
  background: rgba(39, 100, 232, .35);
}

.sidebar.collapsed .sidebar-text,
.sidebar.collapsed nav,
.sidebar.collapsed .account {
  display: none;
}

.sidebar.collapsed .brand {
  justify-content: center;
  margin-top: 36px;
}

.sidebar.collapsed .sidebar-toggle {
  right: 20px;
}

nav {
  display: grid;
  gap: 8px;
}

nav a {
  padding: 11px 12px;
  border-radius: 8px;
  color: #d7dce7;
}

nav a:hover, nav a:focus-visible {
  background: #233047;
  outline: none;
}

.account {
  margin-top: auto;
  border-top: 1px solid #334155;
  padding-top: 18px;
}

main {
  padding: 28px;
  display: grid;
  gap: 22px;
}

body.course-mode main > section:not(.course-shell) {
  display: none;
}

.topbar, .section-title, .top-actions, .runtime-grid {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

h1, h2, p { margin-top: 0; }

h1 {
  max-width: 900px;
  margin-bottom: 0;
  font-size: clamp(2rem, 4vw, 4.5rem);
  line-height: 1;
}

.course-rail h1 {
  font-size: 1.45rem;
  line-height: 1.15;
}

h2 {
  font-size: 1.2rem;
  margin-bottom: 16px;
}

.eyebrow {
  color: var(--accent);
  text-transform: uppercase;
  font-weight: 800;
  font-size: .76rem;
  letter-spacing: 0;
  margin-bottom: 8px;
}

.method-badge {
  display: inline-flex;
  width: fit-content;
  margin: 0 0 8px;
  padding: 6px 10px;
  border-radius: 8px;
  background: #eef4ff;
  color: var(--brand-strong);
  border: 1px solid #9ab4ed;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-weight: 800;
}

.method-help {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  align-items: flex-start;
  margin-bottom: 16px;
}

.info-button {
  font-family: Georgia, serif;
  font-style: italic;
  font-weight: 900;
}

.expected-button {
  font-size: 1rem;
}

.method-info-panel {
  flex-basis: 100%;
  border: 1px solid #9ab4ed;
  border-radius: 8px;
  background: #eef4ff;
  color: var(--ink);
  padding: 14px;
}

.expected-result-panel {
  border-color: #7bbf9e;
  background: #edf8f2;
}

.method-info-panel h3 {
  margin-top: 0;
}

.button, .icon-button {
  border: 0;
  border-radius: 8px;
  background: var(--brand);
  color: #fff;
  font-weight: 800;
  min-height: 42px;
  padding: 0 16px;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.button.secondary, .icon-button {
  background: #e9edf7;
  color: var(--ink);
}

.icon-button {
  width: 42px;
  padding: 0;
  font-size: 1.2rem;
}

.metrics {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 14px;
}

.metrics article, .panel, .lab-card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
}

.metrics article {
  padding: 18px;
}

.metrics span, label span, .lab-card small {
  display: block;
  color: var(--muted);
  font-size: .88rem;
}

.metrics strong {
  display: block;
  margin-top: 8px;
  font-size: 1.45rem;
}

.workspace {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) minmax(330px, .6fr);
  gap: 22px;
}

.course-shell {
  display: grid;
  grid-template-columns: var(--course-rail-width, 320px) minmax(0, 1fr);
  gap: 22px;
  align-items: start;
}

.course-rail, .course-page {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: var(--shadow);
  padding: 18px;
}

.course-rail {
  position: sticky;
  top: 24px;
  max-height: calc(100vh - 48px);
  overflow: auto;
  min-width: 240px;
}

.course-rail-resizer {
  position: absolute;
  top: 0;
  right: -12px;
  width: 14px;
  height: 100%;
  cursor: col-resize;
  z-index: 5;
}

.course-rail-resizer::after {
  content: "";
  position: absolute;
  top: 0;
  left: 6px;
  width: 2px;
  height: 100%;
  background: transparent;
}

.course-rail-resizer:hover::after,
body.course-rail-resizing .course-rail-resizer::after {
  background: var(--brand);
}

.course-nav {
  display: grid;
  gap: 10px;
}

.method-search {
  margin: 12px 0 14px;
  display: grid;
  gap: 6px;
}

.method-search span {
  color: var(--muted);
  font-size: .82rem;
  font-weight: 800;
}

.method-search input {
  min-height: 38px;
}

.empty-search {
  color: var(--muted);
  border: 1px dashed var(--line);
  border-radius: 8px;
  padding: 12px;
}

.course-nav a {
  display: grid;
  grid-template-columns: 34px 1fr;
  gap: 8px;
  color: var(--ink);
  text-decoration: none;
  padding: 9px;
  border-radius: 8px;
  border: 1px solid transparent;
  font-size: .9rem;
}

.course-group {
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.course-group summary {
  cursor: pointer;
  padding: 10px;
  background: #f3f6fb;
  font-weight: 900;
}

.course-group-items {
  display: grid;
  gap: 4px;
  padding: 6px;
}

.course-nav a strong {
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: .84rem;
  overflow-wrap: anywhere;
}

.course-nav a span {
  color: var(--muted);
  font-weight: 800;
}

.course-nav a.active {
  border-color: #9ab4ed;
  background: #eef4ff;
  color: var(--brand-strong);
}

.course-header {
  display: flex;
  align-items: start;
  justify-content: space-between;
  gap: 16px;
  border-bottom: 1px solid var(--line);
  padding-bottom: 14px;
  margin-bottom: 16px;
}

.lesson-counter {
  color: var(--muted);
  font-weight: 800;
}

.lesson-goal {
  color: var(--muted);
  font-size: 1.02rem;
}

.lesson-layout {
  display: grid;
  grid-template-columns: minmax(0, .85fr) minmax(0, 1.15fr);
  gap: 18px;
}

.lesson-steps {
  margin: 0;
  padding-left: 22px;
}

.lesson-steps li {
  margin-bottom: 10px;
}

.lesson-target {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
  min-height: 220px;
  background: #fbfcff;
}

.lesson-box {
  display: grid;
  gap: 12px;
}

.card-stack {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.card-stack strong {
  grid-column: 1 / -1;
}

.code-panel {
  overflow: auto;
  border-radius: 8px;
  border: 1px solid #1f2937;
  background: #111827;
  color: #e5e7eb;
  padding: 16px;
  line-height: 1.55;
}

.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}

.course-actions {
  display: flex;
  justify-content: space-between;
  gap: 12px;
}

.course-actions button:disabled {
  opacity: .45;
  cursor: not-allowed;
}

.method-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}

.method-card {
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 16px;
  display: grid;
  gap: 10px;
  background: color-mix(in srgb, var(--panel) 94%, var(--brand) 6%);
}

.method-card h3 {
  margin: 0;
  font-size: 1rem;
}

.method-name {
  margin: 0;
  color: var(--brand-strong);
  font-weight: 800;
  font-size: .8rem;
}

.method-card fieldset {
  border: 1px solid var(--line);
  border-radius: 8px;
}

.customer-list {
  margin: 0;
  padding: 0;
  list-style: none;
  display: grid;
  gap: 8px;
}

.customer-list li {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 8px 10px;
}

.avatar {
  width: 64px;
  height: 64px;
  border-radius: 8px;
}

.two-column {
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
}

.panel {
  padding: 22px;
}

.lab-list {
  display: grid;
  gap: 12px;
}

.lab-card {
  padding: 16px;
  box-shadow: none;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 12px;
}

.lab-card h3 {
  margin: 4px 0 8px;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.chip {
  background: #edf8f7;
  color: #096b61;
  border: 1px solid #bfe7e2;
  border-radius: 999px;
  padding: 5px 9px;
  font-size: .78rem;
  font-weight: 700;
}

form, .compact {
  display: grid;
  gap: 12px;
}

label {
  display: grid;
  gap: 6px;
  font-weight: 700;
  color: var(--ink);
}

input, select {
  width: 100%;
  border: 1px solid var(--line);
  border-radius: 8px;
  min-height: 40px;
  padding: 8px 10px;
  font: inherit;
  background: #fff;
}

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

.check input {
  width: auto;
}

.drop-zone, .status-card {
  min-height: 76px;
  border: 1px dashed #8aa4dc;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: #f3f7ff;
  color: var(--brand-strong);
  font-weight: 800;
}

.interaction-pad {
  min-height: 180px;
  border: 1px solid #8aa4dc;
  border-radius: 8px;
  display: grid;
  place-items: center;
  background: #eef4ff;
  color: var(--brand-strong);
  font-weight: 800;
  user-select: none;
  touch-action: none;
}

.scroll-pad {
  max-height: 130px;
  overflow: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 12px;
}

.scroll-pad div {
  height: 360px;
}

iframe {
  width: 100%;
  min-height: 92px;
  border: 1px solid var(--line);
  border-radius: 8px;
}

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

th, td {
  text-align: left;
  border-bottom: 1px solid var(--line);
  padding: 12px 8px;
}

dialog {
  border: 1px solid var(--line);
  border-radius: 8px;
  width: min(420px, calc(100vw - 32px));
}

menu {
  display: flex;
  justify-content: flex-end;
  gap: 10px;
  padding: 0;
}

.dark {
  --bg: #0f172a;
  --panel: #172033;
  --ink: #f8fafc;
  --muted: #b9c0cf;
  --line: #334155;
  --shadow: none;
}

.dark input, .dark select {
  background: #111827;
  color: #f8fafc;
}

@media (max-width: 960px) {
  body {
    grid-template-columns: 1fr;
  }

  body.sidebar-collapsed {
    grid-template-columns: 1fr;
  }

  .sidebar {
    position: static;
    height: auto;
    width: auto;
  }

  .sidebar-resizer {
    display: none;
  }

  .workspace, .two-column, .metrics, .method-grid, .course-shell, .lesson-layout {
    grid-template-columns: 1fr;
  }

  .course-rail {
    position: static;
    max-height: none;
  }

  .course-rail-resizer {
    display: none;
  }

  .topbar, .section-title {
    align-items: flex-start;
    flex-direction: column;
  }
}