:root {
  --bg-canvas: #f6f8fa;
  --bg-default: #ffffff;
  --bg-subtle: #f6f8fa;
  --bg-muted: #f1f3f5;
  --border-default: #d0d7de;
  --border-muted: #d8dee4;
  --fg-default: #1f2328;
  --fg-muted: #59636e;
  --fg-on-accent: #ffffff;
  --accent: #0969da;
  --accent-hover: #0860ca;
  --success-bg: #dafbe1;
  --success-fg: #116329;
  --danger-bg: #ffebe9;
  --danger-fg: #cf222e;
  --count-positive-fg: #1f883d;
  --count-negative-fg: #e5534b;
  --changed-bg: #fff8c5;
  --changed-fg: #9a6700;
  --shadow: 0 1px 0 rgba(27, 31, 36, 0.04);
  --radius: 12px;
  --mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: linear-gradient(180deg, #ffffff 0%, var(--bg-canvas) 240px);
  color: var(--fg-default);
  font-family: var(--sans);
}

button,
textarea,
select {
  font: inherit;
}

.service-subtitle {
  margin-top: 8px;
  color: var(--accent);
  font-size: 1rem;
  font-weight: 600;
}

.site-header {
  max-width: 1480px;
  margin: 0 auto;
  padding: 18px 24px 10px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr) minmax(0, 1.2fr);
  gap: 20px;
  align-items: start;
}

.site-intro {
  grid-column: 1 / 3;
}

.header-uses {
  grid-column: 3 / 4;
}

h1,
h2,
p {
  margin: 0;
}

.eyebrow {
  margin: 0 0 8px;
  color: var(--fg-muted);
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  font-size: clamp(1.9rem, 2.7vw, 2.4rem);
  line-height: 1.1;
}

.title-row {
  display: flex;
  align-items: baseline;
  gap: 14px;
  flex-wrap: wrap;
}

.site-copy {
  margin-top: 6px;
  max-width: 840px;
  color: var(--fg-muted);
  line-height: 1.55;
  font-size: 1rem;
}

.header-note {
  margin-top: 8px;
  color: var(--fg-muted);
  font-size: 13px;
  line-height: 1.6;
}

.header-note a {
  color: var(--accent);
  text-decoration: none;
}

.header-note a:hover {
  text-decoration: underline;
}

.header-uses {
  margin-top: 4px;
  padding: 16px;
  border: 0;
  border-radius: var(--radius);
  background: #edf4ff;
  box-shadow: none;
}

.header-uses-title {
  color: var(--accent);
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.02em;
  line-height: 1.3;
}

.header-uses-list {
  margin: 6px 0 0;
  padding: 0;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.header-uses-list li {
  position: relative;
  padding: 0 0 0 18px;
  color: var(--fg-default);
  font-size: 13px;
  line-height: 1.5;
}

.header-uses-list li::before {
  content: "✓";
  position: absolute;
  left: 0;
  top: 0;
  color: var(--accent);
  font-size: 13px;
  font-weight: 700;
  line-height: 1.5;
}

.header-tools {
  margin-top: 12px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
}

.help-button {
  width: 42px;
  height: 42px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border-default);
  border-radius: 12px;
  background: var(--bg-default);
  color: var(--fg-default);
  cursor: pointer;
  box-shadow: var(--shadow);
  font-size: 18px;
  line-height: 1;
}

.mode-toggle {
  display: inline-flex;
  align-items: center;
  height: 42px;
  padding: 4px;
  border: 1px solid var(--border-default);
  border-radius: 12px;
  background: var(--bg-default);
  box-shadow: var(--shadow);
}

.mode-button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  height: 32px;
  border: 0;
  border-radius: 9px;
  padding: 8px 12px;
  background: transparent;
  color: var(--fg-muted);
  cursor: pointer;
  line-height: 1;
}

.mode-button.is-active {
  background: #e8f0fe;
  color: var(--accent);
  font-weight: 600;
}

.help-list {
  margin: 0;
  padding: 0 0 0 22px;
  color: var(--fg-muted);
  line-height: 1.7;
}

.help-accent {
  color: var(--accent);
  font-weight: 600;
}

.app-shell {
  max-width: 1480px;
  margin: 0 auto;
  padding: 0 24px 24px;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr) minmax(0, 1.2fr);
  gap: 20px;
}

.app-shell[data-layout="standard"] {
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr) minmax(0, 1.2fr);
}

.app-shell[data-layout="edit"] {
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
}

.app-shell[data-layout="edit"] .panel-original {
  grid-column: 1 / 2;
  grid-row: 1 / 2;
}

.app-shell[data-layout="edit"] .panel-revised {
  grid-column: 2 / 3;
  grid-row: 1 / 2;
}

.app-shell[data-layout="edit"] .panel-result {
  grid-column: 1 / 3;
  grid-row: 2 / 3;
}

.app-shell[data-layout="review"] {
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
}

.app-shell[data-layout="review"] .panel-original {
  grid-column: 1 / 2;
  grid-row: 1 / 2;
  padding: 10px 0;
  min-width: 42px;
  width: 42px;
  align-items: center;
  justify-content: flex-start;
  z-index: 1;
  background: var(--bg-subtle);
  cursor: pointer;
  transition: background-color 120ms ease, border-color 120ms ease;
}

.app-shell[data-layout="review"] .panel-revised {
  grid-column: 1 / 2;
  grid-row: 1 / 2;
  margin-left: 54px;
}

.app-shell[data-layout="review"] .panel-result {
  grid-column: 2 / 3;
  grid-row: 1 / 2;
}

.app-shell[data-layout="review"] .panel-original .panel-header {
  width: 100%;
  height: 100%;
  justify-content: center;
  align-items: flex-start;
}

.app-shell[data-layout="review"] .panel-original .panel-title-row {
  width: 100%;
  flex-direction: column;
  align-items: center;
  justify-content: flex-start;
  gap: 0;
  padding-top: 6px;
}

.app-shell[data-layout="review"] .panel-original h2 {
  margin: 0 auto;
  writing-mode: vertical-rl;
  text-orientation: mixed;
  transform: rotate(180deg);
  letter-spacing: 0.08em;
}

.app-shell[data-layout="review"] .panel-original:hover {
  background: #eef2f6;
  border-color: #b7c3d0;
}

.app-shell[data-layout="review"] .panel-original:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.app-shell[data-layout="review"] .panel-original .panel-title-sub {
  display: none;
}

.app-shell[data-layout="review"] .panel-original .panel-title-icon {
  display: none;
}

.app-shell[data-layout="review"] .panel-original .panel-count,
.app-shell[data-layout="review"] .panel-original .panel-action,
.app-shell[data-layout="review"] .panel-original textarea,
.app-shell[data-layout="review"] .panel-original .sr-only {
  display: none;
}

.panel {
  min-height: 640px;
  display: flex;
  flex-direction: column;
  gap: 12px;
  padding: 16px;
  border: 1px solid var(--border-default);
  border-radius: var(--radius);
  background: var(--bg-default);
  box-shadow: var(--shadow);
}

.panel-result {
  min-width: 0;
}

.panel-header {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: flex-start;
}

.panel-title-row {
  display: flex;
  align-items: baseline;
  gap: 10px;
  flex-wrap: wrap;
}

.panel-title-row-result {
  gap: 12px;
}

.panel-header h2 {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 1.1rem;
  line-height: 1.3;
}

.panel-title-icon {
  display: inline-flex;
  width: 15px;
  height: 15px;
  color: var(--fg-muted);
  flex: 0 0 auto;
}

.panel-title-icon svg {
  width: 100%;
  height: 100%;
}

.panel-title-sub {
  margin-left: 0;
}

textarea {
  width: 100%;
  border: 1px solid var(--border-default);
  border-radius: 8px;
  background: var(--bg-default);
  color: var(--fg-default);
}

textarea {
  flex: 1;
  min-height: 360px;
  resize: vertical;
  padding: 12px 14px;
  font-family: var(--mono);
  font-size: 14px;
  line-height: 1.55;
}

textarea:focus,
button:focus {
  outline: 2px solid rgba(9, 105, 218, 0.25);
  outline-offset: 2px;
}

.panel-count {
  margin: 0;
  color: var(--fg-muted);
  font-family: var(--mono);
  font-size: 13px;
  line-height: 1.4;
}

.panel-count-delta {
  margin-left: 4px;
  font-weight: 600;
}

.panel-count-delta-positive {
  color: var(--count-positive-fg);
}

.panel-count-delta-negative {
  color: var(--count-negative-fg);
}

.panel-count-delta-neutral {
  color: var(--fg-muted);
}

.panel-action {
  flex-shrink: 0;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border: 1px solid var(--border-default);
  border-radius: 999px;
  padding: 7px 11px;
  background: var(--bg-default);
  color: var(--fg-muted);
  cursor: pointer;
  font-size: 12px;
  line-height: 1;
}

.panel-action:hover {
  background: var(--bg-subtle);
  color: var(--fg-default);
}

.panel-action.is-active {
  border-color: #9ec4f6;
  background: #eaf3ff;
  color: var(--accent);
}

.panel-action.is-success {
  border-color: #7bbd8f;
  background: #eefbf1;
  color: var(--success-fg);
}

.panel-action-icon {
  display: none;
  width: 14px;
  height: 14px;
}

.panel-action-icon svg {
  display: block;
  width: 100%;
  height: 100%;
}

.panel-action.is-active .panel-action-icon {
  display: inline-flex;
}

textarea.is-locked {
  background: #f6f8fa;
  color: #6e7781;
}

.summary-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: baseline;
}

.summary-item {
  display: inline-flex;
  align-items: baseline;
  gap: 4px;
  font-family: var(--mono);
  white-space: nowrap;
}

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

.summary-value {
  color: var(--fg-default);
  font-size: 14px;
  font-weight: 600;
}

.summary-value-added {
  color: var(--count-positive-fg);
}

.summary-value-removed {
  color: var(--count-negative-fg);
}

.diff-output {
  flex: 1;
  min-height: 360px;
  overflow: auto;
  border: 1px solid var(--border-default);
  border-radius: 10px;
  background: var(--bg-subtle);
}

.diff-empty {
  display: grid;
  place-items: center;
  min-height: 100%;
  padding: 24px;
  color: var(--fg-muted);
  text-align: center;
  line-height: 1.7;
}

.diff-row {
  display: grid;
  grid-template-columns: 64px 24px minmax(0, 1fr);
  border-bottom: 1px solid var(--border-muted);
  font-family: var(--mono);
  font-size: 13px;
}

.diff-row-familiar {
  grid-template-columns: 64px minmax(0, 1fr);
}

.diff-row-familiar .diff-sign {
  display: none;
}

.diff-row:last-child {
  border-bottom: 0;
}

.diff-sign {
  display: grid;
  place-items: center;
  padding: 6px 4px;
  color: var(--fg-muted);
  border-right: 1px solid var(--border-muted);
  user-select: none;
}

.diff-line {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  padding: 6px 6px;
  color: #6e7781;
  border-right: 1px solid var(--border-muted);
  font-size: 11px;
  user-select: none;
}

.diff-row-familiar .diff-line {
  justify-content: flex-end;
  padding-right: 10px;
}

.diff-line-before,
.diff-line-after {
  min-width: 18px;
  text-align: right;
}

.diff-line-separator {
  color: #8c959f;
}

.diff-text {
  padding: 6px 10px;
  white-space: pre-wrap;
  word-break: break-word;
  line-height: 1.45;
}

.diff-row-context {
  background: #ffffff;
}

.diff-row-familiar-context {
  background: #ffffff;
}

.diff-row-familiar-changed {
  background: #fffef0;
}

.diff-row-familiar-added {
  background: #f4fff7;
}

.diff-row-familiar-removed {
  background: #fff7f7;
  color: var(--danger-fg);
}

.diff-row-added {
  background: var(--success-bg);
  color: var(--success-fg);
}

.diff-row-added .diff-sign {
  color: var(--success-fg);
}

.diff-row-removed {
  background: var(--danger-bg);
  color: var(--danger-fg);
}

.diff-row-removed .diff-line,
.diff-row-added .diff-line {
  color: inherit;
}

.diff-row-removed .diff-sign {
  color: var(--danger-fg);
}

.inline-added {
  background: rgba(46, 160, 67, 0.22);
  border-radius: 4px;
}

.inline-removed {
  background: rgba(207, 34, 46, 0.18);
  border-radius: 4px;
  text-decoration: line-through;
}

.inline-neutral {
  background: transparent;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.site-footer {
  max-width: 1480px;
  margin: 0 auto;
  padding-left: 24px;
  padding-right: 24px;
}

.seo-sections {
  max-width: 1480px;
  margin: 0 auto;
  padding: 4px 24px 16px;
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
}

.seo-card {
  padding: 16px;
  border: 1px solid var(--border-default);
  border-radius: 14px;
  background: var(--bg-default);
  box-shadow: var(--shadow);
}

.seo-card-wide {
  grid-column: 1 / -1;
}

.seo-card h2 {
  font-size: 1rem;
  line-height: 1.4;
}

.seo-card p,
.seo-list,
.faq-list {
  margin-top: 10px;
  color: var(--fg-muted);
  font-size: 14px;
  line-height: 1.7;
}

.seo-list {
  margin-bottom: 0;
  padding-left: 18px;
}

.faq-list dt {
  color: var(--fg-default);
  font-weight: 600;
}

.faq-list dd {
  margin: 4px 0 10px;
}

.site-footer {
  padding-top: 18px;
  padding-bottom: 40px;
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: center;
  color: var(--fg-muted);
  font-size: 14px;
}

.footer-meta {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.footer-note {
  max-width: 560px;
  font-size: 13px;
  line-height: 1.6;
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.footer-links a {
  color: var(--accent);
  text-decoration: none;
}

.footer-links a:hover {
  text-decoration: underline;
}

.modal-backdrop {
  position: fixed;
  inset: 0;
  display: grid;
  place-items: center;
  padding: 24px;
  background: rgba(31, 35, 40, 0.42);
  z-index: 20;
}

.modal-backdrop[hidden] {
  display: none;
}

.modal-card {
  width: min(640px, 100%);
  max-height: min(80vh, 720px);
  overflow: auto;
  padding: 20px;
  border: 1px solid var(--border-default);
  border-radius: 18px;
  background: var(--bg-default);
  box-shadow: 0 20px 48px rgba(31, 35, 40, 0.16);
}

.modal-header {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: flex-start;
  margin-bottom: 14px;
}

.modal-close {
  width: 36px;
  height: 36px;
  border: 1px solid var(--border-default);
  border-radius: 10px;
  background: var(--bg-default);
  cursor: pointer;
  font-size: 18px;
}

.doc-shell {
  max-width: 960px;
  margin: 0 auto;
  padding: 32px 24px 40px;
}

.doc-back {
  display: inline-block;
  margin-bottom: 18px;
  color: var(--accent);
  text-decoration: none;
}

.doc-back:hover {
  text-decoration: underline;
}

.doc-header {
  margin-bottom: 24px;
}

.doc-card {
  margin-bottom: 16px;
  padding: 20px;
  border: 1px solid var(--border-default);
  border-radius: var(--radius);
  background: var(--bg-default);
  box-shadow: var(--shadow);
}

.doc-card h2 {
  font-size: 1rem;
  line-height: 1.4;
}

.doc-card p {
  margin-top: 10px;
  color: var(--fg-muted);
  line-height: 1.7;
}

.doc-list {
  margin: 10px 0 0;
  padding-left: 18px;
  color: var(--fg-muted);
  line-height: 1.8;
}

.doc-footer {
  padding-left: 0;
  padding-right: 0;
  padding-bottom: 0;
}

@media (max-width: 1180px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .panel {
    min-height: auto;
  }

  textarea,
  .diff-output {
    min-height: 280px;
  }

  .panel-header {
    flex-direction: column;
  }

  .site-header {
    grid-template-columns: 1fr;
  }

  .site-intro,
  .header-uses {
    grid-column: auto;
  }

  .header-uses {
    padding: 10px 12px;
  }

  .app-shell[data-layout="standard"],
  .app-shell[data-layout="edit"],
  .app-shell[data-layout="review"] {
    grid-template-columns: 1fr;
  }

  .app-shell[data-layout="edit"] .panel-original,
  .app-shell[data-layout="edit"] .panel-revised,
  .app-shell[data-layout="edit"] .panel-result {
    grid-column: auto;
    grid-row: auto;
  }

  .seo-sections {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 720px) {
  .site-header,
  .app-shell,
  .seo-sections,
  .site-footer,
  .doc-shell {
    padding-left: 16px;
    padding-right: 16px;
  }

  .site-header {
    padding-top: 24px;
  }

  .title-row {
    flex-direction: column;
    gap: 4px;
    align-items: flex-start;
  }

  .site-footer {
    flex-direction: column;
    align-items: flex-start;
  }
}