:root {
  --bg: #0f172a;
  --panel: #111827;
  --card: #1f2937;
  --text: #e5e7eb;
  --muted: #94a3b8;
  --accent: #38bdf8;
  --border: #243244;
  --input: #0b1220;
}

.theme-light {
  --bg: #f8fafc;
  --panel: #ffffff;
  --card: #ffffff;
  --text: #0f172a;
  --muted: #64748b;
  --accent: #2563eb;
  --border: #e2e8f0;
  --input: #f1f5f9;
}

* { box-sizing: border-box; }

html, body {
  height: 100%;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
}

.skip-link {
  position: absolute;
  left: 12px;
  top: -48px;
  z-index: 10000;
  background: var(--card);
  color: var(--text);
  border: 1px solid var(--accent);
  border-radius: 8px;
  padding: 8px 10px;
}

.skip-link:focus-visible {
  top: 10px;
}

a { color: inherit; text-decoration: none; }

header {
  padding: 16px 24px;
  background: var(--panel);
  display: flex;
  align-items: center;
  gap: 10px;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
}

.header-main-menu {
  position: relative;
  border: 0;
  margin: 0;
  padding: 0;
  flex: 0 0 auto;
  min-width: 0;
  margin-left: auto;
}

.header-main-menu > summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  list-style: none;
  cursor: pointer;
  font-weight: 600;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card);
  color: var(--text);
  padding: 8px 10px;
  margin-top: 6px;
}

.header-main-menu > summary > span:first-child {
  font-size: 16px;
  line-height: 1;
}

.header-main-menu > summary::after {
  content: "▾";
  color: var(--muted);
  font-size: 12px;
}

.header-main-menu:not([open]) > summary::after {
  content: "▸";
}

.header-main-menu > summary:focus-visible,
.sidebar-main-menu > summary:focus-visible,
details.trace > summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.header-main-menu > summary::-webkit-details-marker {
  display: none;
}

.header-main-content {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  z-index: 50;
  width: min(560px, calc(100vw - 32px));
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  box-shadow: 0 12px 24px rgba(2, 6, 23, 0.35);
  display: flex;
  align-items: stretch;
  flex-direction: column;
  gap: 10px;
}

.header-main-menu:not([open]) > .header-main-content {
  display: none;
}

.header-spacer {
  flex: 1 1 auto;
}

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

.logo-mark {
  width: 36px;
  height: 36px;
  color: var(--accent);
}

.logo-text {
  display: flex;
  flex-direction: column;
  line-height: 1.1;
}

.container {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr);
  flex: 1 1 auto;
  min-height: 0;
  align-items: start;
}

.container.full {
  grid-template-columns: 1fr;
  flex: 1 1 auto;
  min-height: 0;
}

.expression-field-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 6px;
  width: 100%;
  flex-wrap: wrap;
}

.freeform-field-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  margin-bottom: 6px;
  width: 100%;
  flex-wrap: wrap;
}

.freeform-field-header label {
  margin: 0;
  min-width: 0;
  flex: 1 1 auto;
}

.freeform-inline-keyboard-field {
  position: relative;
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 8px;
  align-items: start;
  width: 100%;
}

.freeform-inline-keyboard-field > textarea,
.freeform-inline-keyboard-field > input,
.freeform-inline-keyboard-field > select {
  min-width: 0;
  width: 100%;
  grid-column: 1;
}

.freeform-inline-keyboard-field > .math-keyboard-panel {
  grid-column: 2;
  position: relative;
  align-self: start;
}

.freeform-inline-keyboard-field-textarea > .math-keyboard-panel {
  margin-top: 0;
}

.expression-field-header label {
  margin: 0;
  min-width: 0;
  flex: 1 1 auto;
}

.expression-keyboard-row {
  display: flex;
  justify-content: flex-end;
  flex: 0 0 auto;
}

.expression-keyboard-sidebar-row {
  display: flex;
  justify-content: flex-start;
  align-items: flex-start;
  width: 100%;
  margin-top: 6px;
}

.expression-keyboard-sidebar-row .math-keyboard-panel {
  width: auto;
  max-width: 100%;
}

.expression-keyboard-sidebar-row .math-keyboard-panel > summary {
  margin-left: 0;
}

.expression-keyboard-sidebar-row .math-keyboard-panel[open] {
  width: 100%;
}

.expression-keyboard-sidebar-row .math-keyboard {
  max-width: 100%;
}

.freeform-expression-help {
  margin-top: 0;
}

.freeform-hero {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.freeform-hero-copy {
  flex: 1 1 280px;
  min-width: 0;
}

.freeform-page-title,
.freeform-operation-label,
.freeform-result-title {
  margin: 0;
}

.freeform-result-meta {
  display: flex;
  gap: 8px;
  align-items: center;
  margin-top: 4px;
  flex-wrap: wrap;
}

.freeform-result-badge {
  background: #ecfccb;
  color: #365314;
  border-color: #84cc16;
}

.freeform-page-intro {
  margin: 4px 0 0;
}

.freeform-quickstart {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid color-mix(in srgb, var(--border) 78%, transparent);
}

.freeform-quickstart-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  flex-wrap: wrap;
}

.freeform-quickstart-root {
  position: relative;
}

.freeform-quickstart-heading {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 1 1 280px;
  min-width: 0;
  flex-wrap: wrap;
}

.freeform-quickstart-trigger {
  cursor: pointer;
}

.freeform-quickstart-trigger:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 8px;
}

.freeform-quickstart-label {
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.freeform-quickstart-toggle {
  flex: 0 0 auto;
  min-height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}

.freeform-quickstart-body {
  overflow: hidden;
  margin-left: 10px;
  padding-left: 14px;
  border-left: 1px solid color-mix(in srgb, var(--border) 72%, transparent);
}

.freeform-quickstart.is-collapsed .freeform-quickstart-body {
  display: none;
}

.freeform-example-tree {
  margin-top: 0;
}

.freeform-example-root-list {
  margin-top: 0;
  padding-left: 0;
  border-left: 0;
}

.freeform-example-root-list > .tree-node {
  margin-left: 0;
}

.freeform-example-tree-summary {
  letter-spacing: 0.05em;
}

.freeform-example-tree-chips {
  margin-top: 8px;
}

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

.freeform-example-chip {
  border: 1px solid color-mix(in srgb, var(--accent) 48%, var(--border));
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 18%, var(--card)), color-mix(in srgb, var(--card) 90%, transparent));
  color: var(--text);
  border-radius: 999px;
  padding: 8px 12px;
  font-size: 13px;
  line-height: 1.2;
  cursor: pointer;
  transition: transform 140ms ease, border-color 140ms ease, background 140ms ease;
}

.freeform-example-chip:hover,
.freeform-example-chip:focus-visible {
  transform: translateY(-1px);
  border-color: var(--accent);
  background: linear-gradient(135deg, color-mix(in srgb, var(--accent) 26%, var(--card)), color-mix(in srgb, var(--card) 88%, transparent));
}

.freeform-error {
  color: #f87171;
  margin-top: 8px;
}

.freeform-status-card {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.freeform-stale-card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 12px;
  border-color: color-mix(in srgb, #f59e0b 58%, var(--border));
  background: linear-gradient(180deg, color-mix(in srgb, #f59e0b 10%, var(--card)), color-mix(in srgb, var(--card) 92%, var(--panel)));
}

.freeform-stale-card[hidden] {
  display: none !important;
}

.exercise-side.is-stale [data-freeform-solved-card="1"] {
  display: none;
}

.freeform-status-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.freeform-status-details {
  border-top: 1px solid color-mix(in srgb, var(--border) 78%, transparent);
  padding-top: 10px;
}

.freeform-status-details > summary {
  cursor: pointer;
  font-weight: 600;
}

.freeform-status-details > p {
  margin: 10px 0 0;
}

.freeform-solving-card {
  min-height: 250px;
  background: linear-gradient(180deg, color-mix(in srgb, var(--card) 92%, var(--panel)), color-mix(in srgb, var(--panel) 82%, transparent));
}

.exercise-side.is-solving > :not([data-freeform-solving-panel="1"]) {
  display: none;
}

.freeform-solving-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;

  .freeform-quickstart-heading {
    flex: 1 1 100%;
  }
  gap: 12px;
  flex-wrap: wrap;
}


  .freeform-quickstart-toggle {
    width: fit-content;
  }
.freeform-solving-copy {
  margin: 6px 0 0;
}

.freeform-solving-badge {
  background: color-mix(in srgb, var(--accent) 18%, var(--card));
  color: var(--text);
  border-color: color-mix(in srgb, var(--accent) 52%, var(--border));
}

.freeform-solving-steps {
  display: grid;
  gap: 12px;
  margin-top: 16px;
}

.freeform-solving-step {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 12px;
  align-items: flex-start;
  padding: 12px;
  border-radius: 14px;
  border: 1px solid color-mix(in srgb, var(--border) 82%, transparent);
  background: color-mix(in srgb, var(--panel) 76%, transparent);
  opacity: 0.74;
}

.freeform-solving-step.is-active,
.freeform-solving-step.is-complete {
  opacity: 1;
}

.freeform-solving-step.is-active {
  border-color: color-mix(in srgb, var(--accent) 58%, var(--border));
  box-shadow: 0 0 0 1px color-mix(in srgb, var(--accent) 14%, transparent);
}

.freeform-solving-step.is-complete {
  border-color: color-mix(in srgb, #34d399 56%, var(--border));
}

.freeform-solving-step > div > p {
  margin: 4px 0 0;
}

.freeform-solving-step-index {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  font-size: 13px;
  font-weight: 700;
  border: 1px solid color-mix(in srgb, var(--border) 82%, transparent);
  background: color-mix(in srgb, var(--card) 90%, transparent);
}

.freeform-solving-step.is-active .freeform-solving-step-index {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 16%, var(--card));
}

.freeform-solving-step.is-complete .freeform-solving-step-index {
  border-color: #34d399;
  background: color-mix(in srgb, #34d399 18%, var(--card));
}

.freeform-status-copy,
.freeform-status-hint {
  margin: 0;
}

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

.freeform-operation-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  flex-wrap: wrap;
}

.freeform-submit-btn {
  flex: 0 0 auto;
}

.freeform-submit-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  justify-content: flex-end;
}

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

.freeform-share-status {
  min-height: 18px;
}

.freeform-share-status[data-state="error"] {
  color: #f87171;
}

.freeform-share-status[data-state="success"] {
  color: var(--accent);
}

.freeform-expression-footer {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 6px;
  width: 100%;
}

.freeform-expression-footer .freeform-expression-help {
  flex: 1 1 auto;
  min-width: 0;
}

.freeform-live-preview {
  margin-top: 8px;
  padding: 6px 10px;
}

.freeform-live-preview-label {
  margin-bottom: 2px;
}

.freeform-live-preview-body {
  min-height: 28px;
}

.freeform-live-preview-math {
  color: inherit;
}

.freeform-live-preview-math .katex-display {
  margin: 0;
}

.freeform-live-preview-body .katex-display {
  margin: 0.2em 0;
}

.freeform-live-preview-body .katex {
  font-size: 0.95em;
}

.freeform-live-preview-error {
  margin-top: 2px;
  color: #f87171;
}

.freeform-live-preview-error:empty {
  display: none;
}

.freeform-bounds-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px;
}

.freeform-bound-field {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.freeform-bound-input {
  width: 100%;
  min-height: 40px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--input);
  color: var(--text);
  padding: 10px 12px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 14px;
}

.math-keyboard-panel {
  flex: 0 0 auto;
  min-width: 0;
  max-width: 100%;
}

.math-keyboard-panel[open] {
  z-index: 10;
  width: 100%;
  max-width: 100%;
  container-type: inline-size;
}

.freeform-inline-keyboard-field .math-keyboard-panel[open] {
  width: auto;
  max-width: none;
  container-type: normal;
  z-index: 30;
}

.math-keyboard-panel > summary {
  list-style: none;
}

.math-keyboard-panel > summary::-webkit-details-marker {
  display: none;
}

.math-keyboard-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 40px;
  width: 40px;
  height: 40px;
  padding: 0;
  font-size: 18px;
  font-weight: 700;
  border-color: color-mix(in srgb, var(--accent) 60%, var(--border));
  background: color-mix(in srgb, var(--accent) 18%, var(--card));
  box-shadow: 0 6px 14px rgba(2, 6, 23, 0.18);
}

.math-keyboard-toggle-label {
  display: none;
}

.math-keyboard-panel-sidebar > summary {
  width: auto;
}

.math-keyboard-panel-sidebar .math-keyboard-toggle {
  width: auto;
  min-width: 0;
  max-width: 100%;
  height: 32px;
  justify-content: center;
  gap: 8px;
  padding: 0 9px;
  font-size: 12px;
}

.math-keyboard-panel-sidebar .math-keyboard-toggle-label {
  display: inline;
  white-space: nowrap;
}

.math-keyboard-icon {
  width: 20px;
  height: 20px;
  display: block;
}

.math-keyboard-toggle:hover {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 28%, var(--card));
}

.math-keyboard-panel[open] .math-keyboard-toggle {
  border-color: var(--accent);
  background: color-mix(in srgb, var(--accent) 34%, var(--card));
}

.math-keyboard {
  position: static;
  width: 100%;
  max-width: 100%;
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 8px;
  margin-top: 8px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  box-shadow: 0 16px 30px rgba(2, 6, 23, 0.34);
}

.freeform-inline-keyboard-field .math-keyboard {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  width: min(540px, calc(100vw - 48px));
  max-width: min(540px, calc(100vw - 48px));
  min-width: min(320px, calc(100vw - 48px));
}

.math-key-group {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  background: var(--card);
}

.math-key-group[data-key-group="operations"] {
  border-color: color-mix(in srgb, var(--accent) 50%, var(--border));
}

.math-key-group[data-key-group="logs"] {
  border-color: color-mix(in srgb, #f59e0b 50%, var(--border));
}

.math-key-group[data-key-group="trig"] {
  border-color: color-mix(in srgb, #10b981 50%, var(--border));
}

.math-key-group[data-key-group="comparison"] {
  border-color: color-mix(in srgb, #ef4444 50%, var(--border));
}

.math-key-group-basic {
  padding: 8px;
}

.math-key-group-unified {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  padding: 0;
  min-width: 0;
}

.math-key-cluster {
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 8px;
  background: color-mix(in srgb, var(--card) 90%, transparent);
  min-width: 0;
}

.math-key-cluster[data-math-cluster="core"] {
  grid-column: 1 / -1;
}

.math-key-group-title {
  margin-bottom: 6px;
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
}

.math-key-grid {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 5px;
  min-width: 0;
}

.math-key {
  justify-content: center;
  min-height: 30px;
  padding: 4px 6px;
  font-size: 12px;
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
}

@container (max-width: 540px) {
  .math-key-group-unified {
    grid-template-columns: 1fr;
  }

  .math-key-grid {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

@media (max-width: 700px) {
  .math-keyboard {
    width: 100%;
    max-height: none;
    overflow: visible;
  }

  .freeform-inline-keyboard-field .math-keyboard {
    width: min(100vw - 32px, 520px);
    max-width: min(100vw - 32px, 520px);
    min-width: min(280px, 100vw - 32px);
  }

  .math-key-group-unified {
    grid-template-columns: 1fr;
  }
}

.sidebar {
  background: var(--panel);
  border-right: 1px solid var(--border);
  padding: 16px;
  width: 280px;
  min-width: 220px;
  max-width: 520px;
  resize: horizontal;
  overflow: auto;
  overflow-y: auto;
  overflow-x: auto;
  height: 100%;
  max-height: 100%;
  align-self: stretch;
}

.sidebar h3 { margin: 0 0 12px; color: var(--muted); font-size: 14px; }

.sidebar-main-menu {
  position: relative;
  border: 0;
  margin: 0;
  padding: 0;
}

.sidebar-main-menu > summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  list-style: none;
  cursor: pointer;
  font-weight: 600;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--card);
  color: var(--text);
  padding: 8px 10px;
  margin-bottom: 8px;
  min-height: 44px;
  font-size: 14px;
}

.sidebar-main-menu > summary::before {
  content: "≡";
  font-size: 16px;
  line-height: 1;
}

.sidebar-main-menu > summary::after {
  content: "▾";
  color: var(--muted);
  font-size: 12px;
}

.sidebar-main-menu:not([open]) > summary::after {
  content: "▸";
}

.sidebar-main-menu > summary::-webkit-details-marker {
  display: none;
}

.sidebar-main-content {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  right: 0;
  min-width: 280px;
  z-index: 40;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px;
  box-shadow: 0 12px 24px rgba(2, 6, 23, 0.35);
  margin: 0;
}

.sidebar-main-menu:not([open]) > .sidebar-main-content {
  display: none;
}

.sidebar .item {
  padding: 10px 12px;
  border-radius: 8px;
  margin-bottom: 6px;
  background: transparent;
  display: block;
  min-height: 44px;
}

.sidebar .item.active,
.sidebar .item:hover {
  background: var(--card);
}

.main {
  padding: 24px;
  min-width: 0;
  overflow-x: auto;
  overflow-y: auto;
  height: 100%;
  min-height: 0;
}

.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 18px;
  margin-bottom: 16px;
}

.card > h2,
.card > h3 {
  margin-top: 0;
  margin-bottom: 10px;
}

.card > p {
  margin-top: 8px;
}

.card > p.muted {
  margin-bottom: 0;
}

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

.present-top-actions {
  display: flex;
  flex-wrap: nowrap;
  align-items: center;
  gap: 8px;
  flex: 1 1 auto;
  width: 100%;
  min-width: 0;
}

.present-view-nav {
  flex: 1 1 auto;
  min-width: 0;
  width: auto;
  display: flex;
  flex-wrap: nowrap;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.present-view-nav .btn {
  white-space: nowrap;
}

.present-top-actions .present-export-actions {
  margin-left: auto;
  flex: 0 0 auto;
  width: auto;
  display: flex;
  justify-content: flex-end;
}

.present-nav-actions,
.present-exercise-actions {
  overflow: visible;
  width: auto;
}

.present-exercise-actions > .note-crud-popup {
  margin-left: auto;
  flex: 0 0 auto;
}

.tree-group {
  margin-top: 12px;
}

.tree-group.compact {
  margin-top: 8px;
}

.tree-list {
  margin-top: 6px;
}

.tree-node {
  margin: 4px 0 0 12px;
}

.tree-summary {
  font-size: 12px;
  cursor: pointer;
}

.item-plain {
  padding: 0;
  border: 0;
}

.item-nested {
  padding-left: 34px;
}

.row-wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  flex-wrap: wrap;
}

.row-wrap.start {
  align-items: flex-start;
}

.muted-xs {
  font-size: 12px;
}

.mt-4 {
  margin-top: 4px;
}

.mt-6 {
  margin-top: 6px;
}

.mb-4 {
  margin-bottom: 4px;
}

.mb-8 {
  margin-bottom: 8px;
}

.mb-6 {
  margin-bottom: 6px;
}

.opacity-90 {
  opacity: 0.9;
}

.section-divider {
  margin-top: 10px;
  padding-top: 10px;
  border-top: 1px solid rgba(148,163,184,0.25);
}

.controls.spread {
  margin-top: 0;
  margin-bottom: 8px;
  justify-content: space-between;
}

.actions-compact {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

.note-edit-fields,
.method-edit-fields {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.method-edit-fields {
  margin-bottom: 10px;
}

.note-list-summary {
  margin-bottom: 0;
  font-size: 12px;
}

.note-list-table {
  width: 100%;
  border: 1px solid rgba(148,163,184,0.25);
  border-radius: 8px;
  overflow: visible;
}

.note-list-row {
  display: grid;
  grid-template-columns: minmax(260px, 1.25fr) minmax(0, 1.75fr);
  align-items: start;
  gap: 6px;
  padding: 8px;
  border-bottom: 1px solid rgba(148,163,184,0.25);
}

.note-list-summary .note-list-row:first-child {
  border-top: 0;
}

.note-list-summary .note-list-row:last-child {
  border-bottom: 0;
}

.note-col-title {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: start;
  gap: 4px;
  font-weight: 600;
  min-width: 0;
}

.note-title-text {
  display: block;
  min-width: 0;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.note-col-preview {
  min-width: 0;
}

.note-list-actions {
  display: inline-flex;
  align-items: center;
  justify-self: start;
  margin-top: 0;
  flex: 0 0 auto;
}

.note-crud-popup {
  display: inline-block;
  vertical-align: top;
}

.note-divider {
  margin-top: 6px;
  padding-top: 6px;
  border-top: 1px solid rgba(148,163,184,0.25);
}

.notes-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 10px;
  margin-top: 8px;
}

.notes-grid .note-divider {
  margin-top: 0;
  padding: 10px;
  border: 1px solid rgba(148,163,184,0.25);
  border-radius: 10px;
  background: var(--card);
}

.method-list-summary {
  margin-bottom: 10px;
  font-size: 12px;
}

.method-action {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 8px;
}

.method-action > :first-child {
  min-width: 0;
}

.method-action .actions-compact {
  justify-self: end;
  flex-wrap: nowrap;
}

.method-list-summary .row-wrap {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  align-items: center;
  gap: 8px;
}

.method-list-summary .row-wrap > :first-child {
  min-width: 0;
}

.method-list-actions {
  justify-content: flex-end;
  flex-wrap: nowrap;
  margin-left: auto;
}

.method-content-preview,
.method-exercises-block {
  border: 1px solid rgba(148,163,184,0.2);
  border-radius: 8px;
  padding: 8px;
}

.method-exercises-block {
  margin-top: 10px;
}

.method-exercise-row {
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px dashed rgba(148,163,184,0.25);
}

.editor-bottom-nav {
  margin-top: 12px;
}

.is-hidden {
  display: none;
}

.note-crud-popup {
  position: relative;
}

.note-crud-popup > summary {
  list-style: none;
}

.note-crud-popup > summary::-webkit-details-marker {
  display: none;
}

.note-crud-menu {
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  z-index: 20;
  min-width: 180px;
  width: max-content;
  max-width: min(320px, calc(100vw - 24px));
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 8px;
  box-shadow: 0 10px 20px rgba(2, 6, 23, 0.3);
  display: grid;
  gap: 6px;
}

.note-crud-menu .btn {
  width: 100%;
  justify-content: flex-start;
}

.sidebar-lesson-picker {
  position: relative;
  display: flex;
  justify-content: flex-end;
  min-width: 0;
}

.sidebar-lesson-picker .lesson-switch-popup {
  position: static;
}

.sidebar-lesson-picker .lesson-switch-popup > .note-crud-menu {
  top: calc(100% + 6px);
  right: 0;
  left: auto;
  width: min(260px, 100%);
  min-width: 0;
  max-width: calc(100vw - 48px);
}

.note-crud-popup.popup-detached > .note-crud-menu {
  position: fixed;
  top: var(--detached-popup-top, 64px);
  left: var(--detached-popup-left, 12px);
  right: auto;
  width: var(--detached-popup-width, 240px);
  max-width: calc(100vw - 24px);
  z-index: 10060;
}

.lesson-option {
  font-size: 13px;
  font-weight: 500;
  min-height: 32px;
  padding: 0 10px;
}

.lesson-option.is-current {
  border-color: var(--accent);
}

label {
  display: inline-block;
  margin-bottom: 6px;
  color: var(--muted);
  font-size: 13px;
}

.btn {
  background: var(--accent);
  color: #0b1220;
  min-height: 36px;
  padding: 0 14px;
  border-radius: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  font-weight: 600;
  border: 1px solid transparent;
  cursor: pointer;
  position: relative;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color 140ms ease, border-color 140ms ease, color 140ms ease, opacity 140ms ease;
}

button.btn,
a.btn,
select.btn {
  font-family: inherit;
  font-size: 14px;
  line-height: 1;
}

.btn:hover {
  opacity: 0.92;
}

.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

select.btn {
  appearance: none;
  -webkit-appearance: none;
  padding-right: 34px;
  background-image:
    linear-gradient(45deg, transparent 50%, currentColor 50%),
    linear-gradient(135deg, currentColor 50%, transparent 50%);
  background-position: calc(100% - 16px) 55%, calc(100% - 11px) 55%;
  background-size: 5px 5px, 5px 5px;
  background-repeat: no-repeat;
}

.btn.secondary {
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
}

.btn.secondary:hover {
  background: var(--card);
  border-color: var(--accent);
  opacity: 1;
}

.btn.secondary.active {
  background: var(--card);
  border-color: var(--accent);
}

.icon-only-btn {
  min-width: 40px;
  width: 40px;
  padding-left: 0;
  padding-right: 0;
  font-size: 16px;
  line-height: 1;
}

.btn.disabled,
.btn:disabled,
.btn[aria-disabled="true"] {
  opacity: 0.55;
  cursor: not-allowed;
  pointer-events: none;
}

.btn.loading {
  opacity: 0.7;
  pointer-events: none;
}

.btn.loading::after {
  content: "";
  position: absolute;
  right: 10px;
  top: 50%;
  width: 14px;
  height: 14px;
  margin-top: -7px;
  border-radius: 50%;
  border: 2px solid rgba(255, 255, 255, 0.5);
  border-top-color: #fff;
  animation: spin 0.8s linear infinite;
}

/* Icon + label helpers for buttons */
.btn .icon {
  display: inline-flex;
  width: 18px;
  height: 18px;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  line-height: 1;
}

.btn .label {
  display: inline-block;
  margin-left: 8px;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

textarea {
  width: 100%;
  min-height: 520px;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--input);
  color: var(--text);
  padding: 12px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
}

.controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.controls.tight {
  margin-top: 0;
  margin-bottom: 0;
}

.exercise-action-bar {
  justify-content: flex-end;
}

.step {
  border-left: 3px solid var(--accent);
  padding-left: 12px;
  margin-bottom: 10px;
  min-width: 0;
  max-width: 100%;
  overflow: hidden;
}

.step.current {
  border-left-width: 4px;
  background: rgba(56, 189, 248, 0.08);
  padding: 10px 12px;
  border-radius: 8px;
}

details.trace {
  margin: -4px 0 12px 12px;
}

details.trace summary {
  cursor: pointer;
  font-size: 12px;
  color: var(--muted);
}

.trace-text {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 12px;
  margin-top: 6px;
  white-space: pre-wrap;
}

.sympy-form {
  margin-top: 12px;
}

.form-row {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 10px;
}

.radio-group {
  display: flex;
  gap: 20px;
  margin-top: 8px;
  flex-wrap: wrap;
}

.radio-option {
  display: flex;
  align-items: center;
  gap: 6px;
  cursor: pointer;
}

.radio-option input[type="radio"] {
  cursor: pointer;
}

.input {
  border: 1px solid var(--border);
  background: var(--input);
  color: var(--text);
  border-radius: 8px;
  padding: 8px 10px;
  font-size: 14px;
}

.input-full {
  width: 100%;
}

.select-input {
  min-height: 40px;
  width: 100%;
  background: transparent;
  color: inherit;
  border: 1px solid rgba(148,163,184,0.25);
  border-radius: 8px;
  padding: 8px;
}

.textarea-sm {
  min-height: 40px;
}

.textarea-md {
  min-height: 60px;
}

.textarea-note-content {
  min-height: 120px;
}

.textarea-method-content {
  min-height: 140px;
}

.input:focus-visible,
textarea:focus-visible,
select:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-color: var(--accent);
}

.alert-error {
  color: #f87171;
}

.alert-success {
  color: #34d399;
}

.integral-display {
  border: 1px dashed var(--border);
  background: var(--input);
  border-radius: 8px;
  padding: 8px 10px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  font-size: 13px;
}

.exercise-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  align-items: start;
}

.exercise-layout > * {
  min-width: 0;
}

.freeform-layout {
  display: grid;
  width: 100%;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 16px;
  align-items: start;
}

.freeform-layout > .freeform-left,
.freeform-layout > .exercise-side {
  min-width: 0;
}

.freeform-layout > .freeform-left,
.freeform-layout > .exercise-side {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.exercise-side .card {
  position: sticky;
  top: 12px;
}

.freeform-layout .exercise-side .card {
  position: static;
  top: auto;
  width: 100%;
}

.freeform-right-grid {
  display: grid;
  grid-template-columns: calc(50% - 8px) calc(50% - 8px);
  gap: 16px;
  align-items: start;
}

.freeform-result-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.freeform-result-actions {
  margin-left: auto;
  width: auto;
  overflow: visible;
  flex-wrap: nowrap;
}

.freeform-result-actions > .note-crud-popup {
  margin-left: auto;
}

.freeform-result-actions .note-crud-menu {
  left: auto;
  right: 0;
  z-index: 10070;
}

.freeform-result-actions .note-crud-popup {
  margin-left: auto;
}

.freeform-capture-status {
  min-height: 18px;
  margin-top: 8px;
}

.freeform-capture-status[data-state="error"] {
  color: #f87171;
}

.freeform-capture-status[data-state="success"] {
  color: var(--muted);
}

.freeform-solution-capture-mode [data-freeform-capture-hide="1"] {
  visibility: hidden;
}

.freeform-math-block {
  width: 100%;
  min-width: 0;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  -webkit-overflow-scrolling: touch;
}

.freeform-math-block .katex-display {
  display: block;
  max-width: 100%;
  margin: 0;
  padding-bottom: 2px;
  overflow-x: auto;
  overflow-y: hidden;
  -webkit-overflow-scrolling: touch;
}

.freeform-math-block .katex-display > .katex {
  display: block;
  min-width: 0;
  max-width: 100%;
  white-space: normal;
}

.freeform-math-block .katex-display .base {
  white-space: nowrap;
}

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

.item,
.item-plain,
.item-nested,
.tree-summary,
.step,
.trace-text {
  overflow-wrap: anywhere;
  word-break: break-word;
}

.integral-display {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

.kbd {
  border: 1px solid #334155;
  padding: 2px 6px;
  border-radius: 6px;
  background: var(--input);
  font-size: 12px;
}

.badge {
  background: rgba(56, 189, 248, 0.2);
  color: var(--accent);
  border: 1px solid var(--accent);
  padding: 4px 8px;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
}

.homework-card {
  transition: border-color 180ms ease, box-shadow 180ms ease, transform 180ms ease;
}

.homework-card:hover,
.homework-card:focus-visible {
  border-color: var(--accent);
  box-shadow: 0 10px 24px rgba(15, 23, 42, 0.12);
  transform: translateY(-1px);
}

.homework-card-active {
  border-color: var(--accent);
  outline: 2px solid var(--accent);
  box-shadow: 0 12px 28px rgba(56, 189, 248, 0.16);
}

.homework-card-title-row {
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
}

.homework-card-loader {
  display: none;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  font-weight: 600;
  color: var(--muted);
}

.homework-card-loading {
  border-color: var(--accent);
  outline: 2px solid var(--accent);
  box-shadow: 0 12px 28px rgba(56, 189, 248, 0.16);
}

.homework-card-loading .homework-card-loader {
  display: inline-flex;
}

.complexity-badge {
  font-size: 11px;
  padding: 2px 6px;
  vertical-align: middle;
}

.login-main {
  display: flex;
  flex-direction: column;
  justify-content: center;
  min-height: 100%;
  padding-bottom: 72px;
}

.login-card {
  width: min(100%, 620px);
  margin: 0 auto;
}

.controls.login-controls {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 8px;
  align-items: stretch;
}

.controls.login-controls > .login-action {
  width: 100%;
  min-width: 0;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  line-height: 1.2;
  padding: 8px 10px;
  white-space: normal;
  overflow-wrap: anywhere;
}

.controls.login-controls > .login-action-wide {
  grid-column: 1 / -1;
}

.login-guest-form {
  margin-top: 8px;
}

.login-guest-action {
  width: 100%;
  min-height: 44px;
}

.login-password-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

.login-password-input {
  flex: 1 1 auto;
  min-width: 0;
}

.login-footer-note {
  position: fixed;
  left: 0;
  right: 0;
  bottom: max(10px, env(safe-area-inset-bottom));
  text-align: center;
  pointer-events: none;
}

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

@media (max-width: 960px) {
  .container {
    grid-template-columns: 1fr;
    flex: 1 1 auto;
  }
  .container.full {
    flex: 1 1 auto;
  }
  .sidebar {
    border-right: none;
    border-bottom: 1px solid var(--border);
    width: auto;
    max-width: none;
    min-width: 0;
    resize: none;
    height: auto;
    max-height: none;
  }
  .header-main-menu {
    min-width: 0;
    width: auto;
    flex: 0 0 auto;
  }
  .header-main-content {
    width: min(420px, calc(100vw - 24px));
    max-width: calc(100vw - 24px);
    right: 0;
  }
  .header-spacer {
    display: none;
  }
  .sidebar-main-content {
    right: auto;
    width: min(360px, calc(100vw - 24px));
    max-width: calc(100vw - 24px);
    min-width: 0;
  }
  .main {
    height: auto;
    overflow-y: visible;
  }
  .card {
    padding: 14px;
    margin-bottom: 12px;
  }
  .card-header-row {
    align-items: flex-start;
  }
  .exercise-layout {
    grid-template-columns: 1fr;
  }
  .exercise-side .card {
    position: static;
    top: auto;
  }
  .freeform-layout {
    display: grid;
    grid-template-columns: 1fr;
  }
  .freeform-layout > .freeform-left,
  .freeform-layout > .exercise-side {
    width: auto;
  }
  .freeform-right-grid {
    grid-template-columns: 1fr;
  }
  .note-edit-fields,
  .method-edit-fields {
    grid-template-columns: 1fr !important;
  }
  table {
    display: block;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .admin-users-table {
    display: table;
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
  }

  .admin-users-table thead {
    display: none;
  }

  .admin-users-table tbody,
  .admin-users-table tr,
  .admin-users-table td {
    display: block;
    width: 100%;
  }

  .admin-users-table tr {
    border: 1px solid var(--border);
    border-radius: 10px;
    margin-bottom: 10px;
    padding: 8px;
    background: var(--card);
  }

  .admin-users-table td {
    border-bottom: 1px dashed var(--border) !important;
    text-align: left !important;
    padding: 8px 6px !important;
  }

  .admin-users-table td:last-child {
    border-bottom: none !important;
  }

  .admin-users-table td::before {
    content: attr(data-label);
    display: block;
    color: var(--muted);
    font-size: 12px;
    margin-bottom: 4px;
  }

  .admin-users-table td form {
    display: inline-block !important;
    margin: 0;
  }

  .admin-users-table td[data-priority="2"] {
    display: none;
  }

  .admin-users-table tr.is-expanded td[data-priority="2"] {
    display: block;
  }

  .admin-users-toggle {
    display: inline-flex !important;
    margin-right: 6px;
    margin-bottom: 6px;
  }

  .admin-users-actions {
    justify-content: flex-start;
    overflow-x: auto;
    max-width: 100%;
    padding-bottom: 2px;
  }

  .admin-users-table td[data-label="Actions"] {
    display: flex;
    gap: 8px;
    align-items: flex-start;
  }

  .admin-users-table .btn {
    display: inline-block;
    margin: 0;
    width: auto !important;
  }
}

.admin-users-toggle {
  display: none !important;
}

.admin-users-actions {
  display: inline-flex;
  align-items: center;
  justify-content: flex-end;
  gap: 6px;
  flex-wrap: nowrap;
  white-space: nowrap;
}

.admin-users-actions form {
  margin: 0;
}

.admin-users-actions .btn {
  min-width: 160px;
  text-align: center;
  flex: 0 0 auto;
}

.admin-users-actions .admin-users-icon-btn {
  min-width: 40px;
  width: 40px;
  padding-left: 0;
  padding-right: 0;
  font-size: 16px;
  line-height: 1;
}

.admin-users-actions .admin-users-icon-btn svg {
  width: 16px;
  height: 16px;
  display: block;
  margin: 0 auto;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.admin-users-legend {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 14px;
  margin: 8px 0 12px;
  color: var(--muted);
  font-size: 13px;
}

.admin-users-legend-item {
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

.admin-users-legend-icon {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 14px;
  height: 14px;
}

.admin-users-legend-icon svg {
  width: 14px;
  height: 14px;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
}

@media (max-width: 640px) {
  header {
    padding: 12px 16px;
  }
  .sidebar {
    padding: 12px;
  }
  .header-main-menu {
    width: 100%;
    margin-left: 0;
  }
  .header-main-menu > summary {
    width: 100%;
  }
  .header-main-content,
  .sidebar-main-content {
    width: calc(100vw - 24px);
    max-width: calc(100vw - 24px);
    min-width: 0;
  }
  .header-main-content .btn,
  .header-main-content select.btn,
  .header-main-content .header-user {
    width: 100%;
  }
  .main {
    padding: 16px;
  }
  .card > h2,
  .card > h3 {
    line-height: 1.25;
  }
  .card > h2 {
    font-size: 1.15rem;
  }
  .card > h3 {
    font-size: 1rem;
  }
  .card-header-row {
    gap: 8px;
  }
  .card-header-row > * {
    min-width: 0;
  }
  .sidebar-main-menu > summary,
  .sidebar .item {
    min-height: 40px;
  }
  .controls {
    gap: 6px;
    width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
  }
  .btn {
    text-align: center;
    min-height: 40px;
    font-size: 13px;
    padding-left: 10px;
    padding-right: 10px;
  }
  .icon-only-btn {
    min-width: 44px;
    width: 44px;
  }
  .controls .btn {
    flex: 0 0 auto;
    white-space: nowrap;
  }
  .login-main {
    justify-content: flex-start;
    padding-bottom: 84px;
  }
  .login-card {
    width: 100%;
    margin: 0;
  }
  .login-card .controls {
    width: 100%;
    overflow: visible;
  }
  .login-card .controls.login-controls {
    display: grid;
    grid-template-columns: 1fr;
    align-items: stretch;
  }
  .login-card .controls.login-controls > .login-action {
    min-height: 44px;
    justify-content: center;
    white-space: normal;
    width: 100%;
    min-width: 0;
  }
  .login-guest-form {
    margin-top: 6px;
  }
  .login-guest-action {
    width: 100%;
  }
  .login-footer-note {
    font-size: 11px;
    bottom: max(8px, env(safe-area-inset-bottom));
    padding: 0 12px;
  }
  .note-crud-popup {
    position: relative;
  }
  .note-crud-menu {
    left: 0;
    right: auto;
    width: min(320px, calc(100vw - 24px));
    max-width: calc(100vw - 24px);
    max-height: 60vh;
    overflow: auto;
    padding: 6px;
  }
  .method-action,
  .method-action .actions-compact,
  .method-list-actions,
  .method-exercise-row .row-wrap,
  .exercise-action-bar {
    overflow: visible;
  }
  .method-action .note-crud-menu,
  .method-list-actions .note-crud-menu,
  .method-exercise-row .row-wrap > .note-crud-popup > .note-crud-menu,
  .exercise-action-bar .note-crud-menu,
  .actions-compact .note-crud-menu {
    left: auto;
    right: 0;
  }
  .sidebar-lesson-picker,
  .present-export-actions,
  .present-nav-actions,
  .present-exercise-actions,
  .export-view-actions,
  .export-exercise-view-actions {
    overflow: visible;
    width: auto;
  }
  .present-export-actions .note-crud-popup:not(.popup-detached) > .note-crud-menu,
  .present-nav-actions .note-crud-popup:not(.popup-detached) > .note-crud-menu,
  .present-exercise-actions .note-crud-popup:not(.popup-detached) > .note-crud-menu,
  .export-view-actions .note-crud-popup:not(.popup-detached) > .note-crud-menu,
  .export-exercise-view-actions .note-crud-popup:not(.popup-detached) > .note-crud-menu {
    left: auto;
    right: 0;
  }
  .note-crud-menu .btn {
    white-space: normal;
    min-height: 34px;
    font-size: 13px;
  }
  .present-top-actions {
    width: 100%;
    display: flex;
    flex-wrap: nowrap;
    align-items: center;
  }
  .present-nav-actions,
  .present-exercise-actions {
    width: 100%;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
    flex-wrap: nowrap;
  }
  .present-exercise-actions {
    justify-content: flex-start;
  }
  .present-nav-actions .btn,
  .present-exercise-actions .btn {
    flex: 0 0 auto;
    white-space: nowrap;
  }
  .present-view-nav {
    width: auto;
    flex: 1 1 auto;
    display: flex;
    flex-wrap: nowrap;
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }
  .present-top-actions .present-export-actions {
    margin-left: auto;
    flex: 0 0 auto;
    justify-content: flex-end;
  }
  .present-export-actions > .note-crud-popup,
  .present-exercise-actions > .note-crud-popup {
    margin-left: auto;
  }
  .freeform-result-bar {
    flex-wrap: nowrap;
  }
  .freeform-result-actions {
    width: auto;
    overflow: visible;
    margin-left: auto;
    flex-wrap: nowrap;
  }
  .freeform-result-actions .note-crud-menu {
    left: auto;
    right: 0;
  }
  .badge {
    font-size: 11px;
    padding: 3px 6px;
  }
  .step {
    padding-left: 10px;
  }
  textarea {
    min-height: 180px;
  }
}

.badge-integral { background: #dbeafe; color: #1e40af; }
.badge-derivative { background: #fce7f3; color: #9d174d; }

@media (max-width: 520px) {
  .card {
    padding: 12px;
  }
  .freeform-layout > .exercise-side,
  .freeform-layout > .exercise-side .card,
  .freeform-layout > .exercise-side .step,
  .freeform-layout > .exercise-side .step.current {
    min-width: 0;
    max-width: 100%;
    overflow-x: hidden;
  }
  .freeform-math-block {
    max-width: calc(100vw - 32px);
  }
  .freeform-math-block .katex-display {
    font-size: 0.88em;
  }
  .freeform-hero,
  .freeform-operation-bar,
  .freeform-result-bar,
  .freeform-solving-header,
  .freeform-quickstart-header {
    align-items: stretch;
  }
  .freeform-operation-bar,
  .freeform-result-bar,
  .freeform-solving-header {
    flex-direction: column;
  }
  .freeform-submit-btn,
  .freeform-result-actions {
    width: 100%;
  }
  .freeform-submit-btn {
    justify-content: center;
  }
  .freeform-result-actions {
    margin-left: 0;
    justify-content: flex-start;
    overflow: visible;
  }
  .freeform-result-actions > .note-crud-popup,
  .freeform-result-actions .note-crud-popup {
    margin-left: 0;
  }
  .freeform-result-actions .note-crud-menu {
    left: 0;
    right: auto;
    width: min(320px, calc(100vw - 32px));
    max-width: calc(100vw - 32px);
  }
  .freeform-status-actions > .btn,
  .freeform-example-chip {
    width: 100%;
    justify-content: center;
  }
  .freeform-expression-footer {
    flex-direction: column;
    align-items: stretch;
    gap: 8px;
  }
  .freeform-expression-footer .expression-keyboard-row,
  .freeform-expression-footer .expression-keyboard-row:has(.math-keyboard-panel[open]) {
    width: 100%;
    margin-left: 0;
    justify-content: flex-start;
  }
  .freeform-expression-footer .math-keyboard-panel[open] {
    justify-items: stretch;
  }
  .freeform-expression-footer .math-keyboard-panel[open] > summary {
    width: fit-content;
  }
  .login-main {
    padding-bottom: 72px;
  }
  .login-card {
    border-radius: 10px;
  }
  .login-password-row {
    gap: 6px;
  }
  .login-card .controls.login-controls {
    gap: 8px;
  }
  .login-card .controls.login-controls > .login-action,
  .login-guest-action {
    font-size: 14px;
    line-height: 1.25;
    padding: 10px 12px;
  }
  .login-footer-note {
    position: static;
    margin-top: 14px;
    padding: 0 6px;
  }
  .sidebar .item {
    padding: 8px 10px;
  }
  .present-nav-actions,
  .present-exercise-actions {
    position: sticky;
    top: 0;
    z-index: 6;
    background: var(--card);
    padding: 4px 0;
  }
}

@media (max-width: 700px) {
  .freeform-layout {
    gap: 12px;
  }
  .freeform-math-block .katex-display {
    font-size: 0.94em;
  }
  .freeform-bounds-grid {
    grid-template-columns: 1fr;
  }
  .freeform-result-bar {
    flex-wrap: wrap;
  }
  .freeform-expression-footer .freeform-expression-help {
    flex-basis: 100%;
  }
  .freeform-expression-footer .expression-keyboard-row {
    flex: 1 0 100%;
  }
  .freeform-expression-footer .math-keyboard-panel[open] .math-keyboard {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }
}

@media print {
  header, .no-print { display: none !important; }
  body { background: #fff !important; color: #000 !important; }
  .card, .no-print-border {
    border: none !important;
    box-shadow: none !important;
    background: transparent !important;
  }
  .container { max-width: 100% !important; }
  .step { background: #f8fafc !important; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
}