:root {
  --bg-color: #0d1117;
  --panel-bg: #161b22;
  --border-color: #30363d;
  --text-primary: #c9d1d9;
  --text-secondary: #8b949e;
  --accent-color: #58a6ff;
  --success-color: #238636;
  --error-color: #f85149;
  
  --match-bg-1: rgba(84, 174, 255, 0.25);
  --match-border-1: rgba(84, 174, 255, 0.4);
  --match-bg-2: rgba(46, 160, 67, 0.25);
  --match-border-2: rgba(46, 160, 67, 0.4);
  
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-mono: 'Fira Code', ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

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

body {
  font-family: var(--font-sans);
  background-color: var(--bg-color);
  color: var(--text-primary);
  line-height: 1.5;
  min-height: 100vh;
}

.code-font {
  font-family: var(--font-mono);
  font-size: 14px;
}

/* Scrollbars */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg-color);
}
::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--text-secondary);
}

/* Layout */
.app-container {
  display: grid;
  grid-template-columns: 1fr 350px;
  min-height: 100vh;
  max-width: 1400px;
  margin: 0 auto;
}

@media (max-width: 900px) {
  .app-container {
    grid-template-columns: 1fr;
  }
  .sidebar {
    border-left: none;
    border-top: 1px solid var(--border-color);
  }
}

.main-content {
  padding: 2rem;
  display: flex;
  flex-direction: column;
  gap: 2rem;
  overflow-y: auto;
}

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

.header-left h1 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-top: 0.5rem;
}

.back-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.2s;
}

.back-link:hover {
  color: var(--accent-color);
}

.header-right p {
  color: var(--text-secondary);
  font-size: 0.875rem;
}

/* Inputs */
.input-group label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 0.5rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.regex-field-wrapper {
  display: flex;
  align-items: center;
  background-color: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 0 0.5rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.regex-field-wrapper:focus-within {
  border-color: var(--accent-color);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.2);
}

.regex-field-wrapper.has-error {
  border-color: var(--error-color);
  box-shadow: 0 0 0 3px rgba(248, 81, 73, 0.2);
}

.regex-slash {
  color: var(--text-secondary);
  font-family: var(--font-mono);
  font-size: 1.25rem;
  user-select: none;
  padding: 0 0.25rem;
}

input[type="text"] {
  background: transparent;
  border: none;
  color: var(--text-primary);
  padding: 0.75rem 0.5rem;
  outline: none;
  width: 100%;
}

#regex-input {
  flex-grow: 1;
  color: var(--accent-color);
}

#regex-flags {
  width: 4rem;
  color: #df8e1d;
}

.error-message {
  color: var(--error-color);
  font-size: 0.875rem;
  margin-top: 0.5rem;
  min-height: 1.25rem;
  font-family: var(--font-mono);
}

/* Test String Area */
.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.section-header h2, .results-section h2 {
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 500;
  margin-bottom: 0.5rem;
}

.badge {
  background-color: var(--panel-bg);
  border: 1px solid var(--border-color);
  padding: 0.125rem 0.5rem;
  border-radius: 12px;
  font-size: 0.75rem;
  font-weight: 500;
  color: var(--text-secondary);
}

.badge.has-matches {
  color: var(--success-color);
  border-color: var(--success-color);
  background-color: rgba(35, 134, 54, 0.1);
}

.editor-container {
  position: relative;
  background-color: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  height: 250px;
  overflow: hidden;
}

.editor-container:focus-within {
  border-color: var(--accent-color);
}

#test-string-input, #test-string-highlight {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  padding: 1rem;
  margin: 0;
  border: none;
  background: transparent;
  white-space: pre-wrap;
  word-wrap: break-word;
  overflow-y: auto;
  line-height: 1.6;
}

#test-string-input {
  color: var(--text-primary);
  /* The trick: text is visible but highlighting happens behind it */
  color: transparent; 
  caret-color: var(--text-primary);
  z-index: 2;
  resize: none;
  outline: none;
}

#test-string-highlight {
  color: var(--text-primary);
  z-index: 1;
  pointer-events: none;
}

/* Match Highlighting */
.match {
  border-radius: 3px;
  display: inline-block;
  line-height: 1;
  padding: 2px 0;
  margin: -2px 0;
  border-bottom: 2px solid transparent;
}

.match-even {
  background-color: var(--match-bg-1);
  border-bottom-color: var(--match-border-1);
}

.match-odd {
  background-color: var(--match-bg-2);
  border-bottom-color: var(--match-border-2);
}

/* Results Section */
.results-container {
  background-color: var(--panel-bg);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 1rem;
  min-height: 100px;
  max-height: 250px;
  overflow-y: auto;
}

.empty-state {
  color: var(--text-secondary);
  font-style: italic;
  font-size: 0.875rem;
  text-align: center;
  padding: 2rem 0;
}

.match-result-item {
  padding: 0.5rem;
  border-bottom: 1px dashed var(--border-color);
  display: flex;
  gap: 1rem;
}

.match-result-item:last-child {
  border-bottom: none;
}

.match-index {
  color: var(--text-secondary);
  font-size: 0.75rem;
  width: 2rem;
  flex-shrink: 0;
  padding-top: 0.2rem;
}

.match-value {
  color: var(--accent-color);
  word-break: break-all;
}

.match-groups {
  margin-top: 0.25rem;
  font-size: 0.8rem;
  color: var(--text-secondary);
  padding-left: 0.5rem;
  border-left: 2px solid var(--border-color);
}

.match-group-item strong {
  color: #df8e1d;
  font-weight: normal;
}

/* Sidebar Cheatsheet */
.sidebar {
  background-color: var(--panel-bg);
  border-left: 1px solid var(--border-color);
  padding: 0;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  height: 100vh;
}

.sidebar h2 {
  font-size: 1rem;
  padding: 1.5rem;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  background-color: var(--panel-bg);
  z-index: 10;
}

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

.cheat-group:last-child {
  border-bottom: none;
}

.cheat-group h3 {
  font-size: 0.875rem;
  color: var(--text-secondary);
  margin-bottom: 0.75rem;
  font-weight: 500;
}

.cheat-group ul {
  list-style-type: none;
}

.cheat-group li {
  font-size: 0.875rem;
  margin-bottom: 0.5rem;
  display: flex;
  align-items: baseline;
  color: var(--text-primary);
}

.cheat-group code {
  font-family: var(--font-mono);
  background-color: rgba(255, 255, 255, 0.1);
  padding: 0.125rem 0.375rem;
  border-radius: 4px;
  font-size: 0.75rem;
  margin-right: 0.75rem;
  color: var(--accent-color);
  min-width: 2.5rem;
  text-align: center;
  display: inline-block;
}