:root {
  color-scheme: light dark;
  --bg: light-dark(#f5f5f5, #1c1c1e);
  --panel: light-dark(#ffffff, #2c2c2e);
  --text: light-dark(#1f1f1f, #f2f2f7);
  --border: light-dark(#e0e0e0, #3a3a3c);
  --accent: #2563eb;
  --added: #16a34a1a;
  --added-border: #16a34a;
  --removed: #dc26261a;
  --removed-border: #dc2626;
  --unchanged: #94a3b81a;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: "SF Pro Display", "Segoe UI", system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  display: flex;
  flex-direction: column;
}

a {
  color: var(--accent);
}

.app-header,
.app-footer {
  padding: 1.5rem clamp(1rem, 4vw, 4rem);
}

.app-header {
  text-align: center;
}

.brand {
  display: inline-flex;
  gap: 1.5rem;
  align-items: center;
  text-align: left;
  margin-top: -0.90rem;
}

.brand-logo {
  width: 88px;
  height: 80px;
  object-fit: contain; text-align: left;
  filter: drop-shadow(0 6px 19px #00000022);
}

.tagline {
  margin-top: -1rem;
}

.app-main {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 1rem;
  padding: 0 clamp(1rem, 4vw, 4rem) 2rem;
}

.input-panel {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1rem;
}

.textarea-wrapper {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

textarea {
  width: 100%;
  min-height: 220px;
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  padding: 1rem;
  background: var(--panel);
  color: var(--text);
  font-family: "JetBrains Mono", "Fira Code", monospace;
  font-size: 0.95rem;
  resize: vertical;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  align-items: center;
  justify-content: flex-end;
}

button {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.65rem 1.25rem;
  background: var(--panel);
  color: var(--text);
  font-weight: 600;
  cursor: pointer;
  transition: transform 80ms ease, border-color 150ms ease;
}

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

button:active {
  transform: scale(0.97);
}

.inline-checkbox {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.9rem;
}

.output-panel {
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  background: var(--panel);
  padding: 1rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.summary-header {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1rem;
  align-items: center;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border);
}

.summary-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin: 0;
}

.summary-subtitle {
  margin: 0.15rem 0 0;
  opacity: 0.75;
}

.summary-stats {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.stat {
  min-width: 80px;
  text-align: center;
}

.stat span {
  display: block;
  font-size: 1.2rem;
  font-weight: 700;
}

.stat label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  opacity: 0.7;
}

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
}

.legend-item {
  padding: 0.35rem 0.75rem;
  border-radius: 999px;
  font-size: 0.8rem;
  border: 1px solid transparent;
}

.legend-item.added {
  background: var(--added);
  border-color: var(--added-border);
}

.legend-item.removed {
  background: var(--removed);
  border-color: var(--removed-border);
}

.legend-item.unchanged {
  background: var(--unchanged);
  border-color: var(--border);
}

.diff-output {
  display: flex;
  flex-wrap: nowrap;
  gap: 1rem;
  overflow-x: auto;
  padding-bottom: 0.5rem;
  font-family: "JetBrains Mono", "Fira Code", monospace;
  font-size: 0.75rem;
}

.diff-output::-webkit-scrollbar {
  height: 6px;
}

.diff-output::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 999px;
}

.diff-output::-webkit-scrollbar-track {
  background: transparent;
}

.diff-panel {
  border: 1px solid var(--border);
  border-radius: 0.75rem;
  background: light-dark(#ffffff, #161616);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  min-width: min(420px, 100%);
}

.diff-panel h3 {
  margin: 0;
  padding: 0.65rem 1rem;
  border-bottom: 1px solid var(--border);
  background: light-dark(#f8fafc, #111113);
  font-size: 0.95rem;
}

.diff-lines {
  padding: 0.25rem 0;
  overflow-x: auto;
  overflow-y: visible;
  max-height: none;
  white-space: pre;
}

.diff-lines::-webkit-scrollbar {
  height: 6px;
}

.diff-lines::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 999px;
}

.diff-lines::-webkit-scrollbar-track {
  background: transparent;
}

.diff-line {
  display: flex;
  gap: 0.5rem;
  padding: 0.1rem 0.9rem;
  align-items: flex-start;
  white-space: pre-wrap;
  word-break: break-word;
  overflow-wrap: anywhere;
}

.diff-line.added {
  background: var(--added);
  border-left: 4px solid var(--added-border);
}

.diff-line.removed {
  background: var(--removed);
  border-left: 4px solid var(--removed-border);
}

.diff-line.unchanged {
  background: transparent;
  border-left: 4px solid transparent;
}

.diff-line.blank-line {
  display: none;
}

.diff-line .line-number {
  opacity: 0.65;
  font-variant-numeric: tabular-nums;
  line-height: 1.3;
  min-width: 2.5rem;
  display: inline-flex;
  justify-content: flex-end;
  align-items: flex-start;
  user-select: none !important;
  -webkit-user-select: none !important;
  -moz-user-select: none !important;
  -ms-user-select: none !important;
  pointer-events: none;
}

.diff-line pre {
  margin: 0;
  line-height: 1.3;
  flex: 1;
  white-space: pre;
  user-select: text;
  -webkit-user-select: text;
  -moz-user-select: text;
  -ms-user-select: text;
}

.merge-btn {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.1rem 0.75rem;
  font-size: 0.7rem;
  background: light-dark(#f8fafc, #111113);
  color: inherit;
  cursor: pointer;
  white-space: nowrap;
  display: inline-flex;
  align-items: center;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  gap: 0.2rem;
}

.merge-btn.to-right {
  border-color: var(--added-border);
  color: var(--added-border);
}

.merge-btn.to-left {
  border-color: var(--removed-border);
  color: var(--removed-border);
}

.line-actions {
  display: inline-flex;
  gap: 0.35rem;
  margin-left: 0.5rem;
  opacity: 0;
  transition: opacity 0.15s ease;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
}

.diff-line:hover .line-actions {
  opacity: 1;
}

.delete-btn {
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 0.1rem 0.6rem;
  font-size: 0.7rem;
  background: transparent;
  color: light-dark(#b91c1c, #fca5a5);
  cursor: pointer;
  white-space: nowrap;
  user-select: none;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
}

.placeholder {
  text-align: center;
  padding: 2rem;
  opacity: 0.7;
}

@media (max-width: 640px) {
  .diff-side {
    grid-template-columns: 2.25rem 1fr;
    padding: 0.4rem 0.5rem;
  }
}