:root {
  --bg-color: #0d1117;
  --panel-bg: #161b22;
  --border-color: #30363d;
  --text-color: #c9d1d9;
  --text-muted: #8b949e;
  --primary-color: #238636;
  --primary-hover: #2ea043;
  --error-color: #f85149;
  --match-bg: rgba(35, 134, 54, 0.4);
  --match-border: #238636;
  --group-1: #58a6ff;
  --group-2: #d2a8ff;
  --group-3: #ff7b72;
  --group-4: #ffa657;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background-color: var(--bg-color);
  color: var(--text-color);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  line-height: 1.5;
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

header {
  padding: 1rem 2rem;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

h1 {
  font-size: 1.25rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

main {
  display: flex;
  flex: 1;
  overflow: hidden;
}

.editor-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  border-right: 1px solid var(--border-color);
}

.regex-section {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.input-group {
  margin-bottom: 1rem;
}

label {
  display: block;
  margin-bottom: 0.5rem;
  font-size: 0.875rem;
  color: var(--text-muted);
}

.regex-input-wrapper {
  display: flex;
  align-items: center;
  background: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 0.5rem;
}

.regex-slash {
  color: var(--text-muted);
  font-family: var(--font-mono);
  padding: 0 0.5rem;
}

#regex-input {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--text-color);
  font-family: var(--font-mono);
  font-size: 1rem;
  outline: none;
}

#flags-input {
  width: 60px;
  background: transparent;
  border: none;
  color: var(--text-color);
  font-family: var(--font-mono);
  font-size: 1rem;
  outline: none;
  border-left: 1px solid var(--border-color);
  padding-left: 0.5rem;
}

.error-message {
  color: var(--error-color);
  font-size: 0.875rem;
  margin-top: 0.5rem;
  display: none;
}

.replace-section {
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
  display: none;
}

.replace-section.active {
  display: block;
}

#replace-input {
  width: 100%;
  background: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 0.5rem;
  color: var(--text-color);
  font-family: var(--font-mono);
  outline: none;
}

.test-section {
  flex: 1;
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
}

.test-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.test-strings-container {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.test-case {
  background: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  display: flex;
  flex-direction: column;
}

.test-case-header {
  display: flex;
  justify-content: space-between;
  padding: 0.5rem 1rem;
  border-bottom: 1px solid var(--border-color);
  font-size: 0.75rem;
  color: var(--text-muted);
}

.test-case-content {
  position: relative;
  min-height: 100px;
}

.test-input, .test-backdrop {
  width: 100%;
  height: 100%;
  min-height: 100px;
  padding: 1rem;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  line-height: 1.5;
  white-space: pre-wrap;
  word-wrap: break-word;
  position: absolute;
  top: 0;
  left: 0;
  border: none;
  outline: none;
  background: transparent;
}

.test-input {
  color: transparent;
  caret-color: var(--text-color);
  z-index: 2;
  resize: vertical;
}

.test-backdrop {
  color: var(--text-color);
  z-index: 1;
  overflow: hidden;
}

.match-highlight {
  background-color: var(--match-bg);
  border-bottom: 2px solid var(--match-border);
  border-radius: 2px;
}

.replaced-text {
  color: var(--group-1);
}

.pass-fail-indicator {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  display: inline-block;
  margin-right: 0.5rem;
}

.pass { background-color: var(--primary-color); }
.fail { background-color: var(--error-color); }

.sidebar {
  width: 350px;
  display: flex;
  flex-direction: column;
  border-left: 1px solid var(--border-color);
  background: var(--bg-color);
}

.sidebar-tabs {
  display: flex;
  border-bottom: 1px solid var(--border-color);
}

.tab-btn {
  flex: 1;
  padding: 0.75rem;
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 0.875rem;
  border-bottom: 2px solid transparent;
}

.tab-btn.active {
  color: var(--text-color);
  border-bottom-color: var(--primary-color);
}

.sidebar-content {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
}

.cheat-sheet-section {
  margin-bottom: 1.5rem;
}

.cheat-sheet-section h3 {
  font-size: 0.875rem;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.cheat-item {
  display: flex;
  justify-content: space-between;
  padding: 0.25rem 0;
  font-size: 0.875rem;
}

.cheat-token {
  font-family: var(--font-mono);
  color: var(--group-1);
}

.cheat-desc {
  color: var(--text-muted);
  text-align: right;
}

.match-info-card {
  background: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 0.75rem;
  margin-bottom: 0.75rem;
}

.match-info-header {
  display: flex;
  justify-content: space-between;
  margin-bottom: 0.5rem;
  font-size: 0.875rem;
}

.group-tag {
  display: inline-block;
  padding: 0.1rem 0.4rem;
  border-radius: 4px;
  font-size: 0.75rem;
  font-family: var(--font-mono);
  margin-right: 0.5rem;
  margin-bottom: 0.25rem;
}

.group-1 { background: rgba(88, 166, 255, 0.2); color: #58a6ff; }
.group-2 { background: rgba(210, 168, 255, 0.2); color: #d2a8ff; }
.group-3 { background: rgba(255, 123, 114, 0.2); color: #ff7b72; }

.btn {
  padding: 0.5rem 1rem;
  border-radius: 6px;
  font-size: 0.875rem;
  cursor: pointer;
  border: 1px solid var(--border-color);
  background: var(--panel-bg);
  color: var(--text-color);
  transition: all 0.2s;
}

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

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

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

.controls {
  display: flex;
  gap: 0.5rem;
}

.stat-item {
  font-size: 0.75rem;
  color: var(--text-muted);
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.library-item {
  padding: 0.75rem;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  margin-bottom: 0.5rem;
  cursor: pointer;
  transition: background 0.2s;
}

.library-item:hover {
  background: var(--panel-bg);
}

.library-name {
  font-weight: 600;
  font-size: 0.875rem;
  margin-bottom: 0.25rem;
}

.library-pattern {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

@media (max-width: 768px) {
  main {
    flex-direction: column;
  }
  .sidebar {
    width: 100%;
    height: 300px;
    border-left: none;
    border-top: 1px solid var(--border-color);
  }
}