:root {
  --bg: #0f1115;
  --panel: #171a21;
  --panel-2: #1e222b;
  --fg: #e6e8ec;
  --muted: #8a93a6;
  --accent: #c5a3ff;
  --accent-2: #7cc4ff;
  --border: #272b35;
  --error: #ff6b6b;
  --match-bg: rgba(197, 163, 255, 0.25);
  --match-border: #c5a3ff;

  --literal-color: #9ae6b4;
  --predefined-color: #7cc4ff;
  --charclass-color: #f5c26b;
  --anchor-color: #ff9ec7;
  --group-color: #c5a3ff;
  --quantifier-color: #8a93a6;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Hiragino Sans",
    "Hiragino Kaku Gothic ProN", Meiryo, sans-serif;
  font-size: 15px;
  line-height: 1.6;
}

header {
  padding: 24px 32px 8px;
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  gap: 8px;
  border-bottom: 1px solid var(--border);
}
header h1 {
  margin: 0;
  font-size: 22px;
}
header #subtitle {
  grid-column: 1 / 2;
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 14px;
}
.lang-switch {
  grid-column: 2 / 3;
  grid-row: 1 / 3;
  display: flex;
  align-items: center;
  gap: 6px;
}

main {
  padding: 24px 32px 48px;
  max-width: 1200px;
  margin: 0 auto;
}
section { margin-bottom: 28px; }

h2 {
  font-size: 12px;
  color: var(--muted);
  font-weight: 600;
  margin: 0 0 10px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.sub-heading { margin-top: 16px; }

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

.row { display: flex; gap: 14px; align-items: flex-end; }
.col { display: flex; flex-direction: column; }
.flex-1 { flex: 1; }

input[type="text"], textarea {
  width: 100%;
  padding: 10px 12px;
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 15px;
  line-height: 1.5;
  resize: vertical;
}
input[type="text"]:focus, textarea:focus {
  outline: none;
  border-color: var(--accent);
}
.flags-field { width: 80px; }

select {
  padding: 8px 10px;
  background: var(--panel-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  color: var(--fg);
  font-size: 14px;
}

.error {
  margin-top: 12px;
  color: var(--error);
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 13px;
}

.tree-output {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 24px;
  overflow-x: auto;
  min-height: 120px;
}

/* Tree nodes -------------------------------------------------------- */

.rv-node {
  display: inline-block;
  vertical-align: top;
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 13px;
  margin: 2px;
}

.rv-literal, .rv-predefined, .rv-anchor, .rv-charClass {
  padding: 8px 12px;
  border-radius: 6px;
  background: var(--panel-2);
  border: 1px solid var(--border);
  color: var(--fg);
}

.rv-literal { border-left: 3px solid var(--literal-color); }
.rv-predefined { border-left: 3px solid var(--predefined-color); color: var(--predefined-color); }
.rv-charClass { border-left: 3px solid var(--charclass-color); color: var(--charclass-color); }
.rv-anchor { border-left: 3px solid var(--anchor-color); color: var(--anchor-color); }

.rv-sequence { }
.rv-sequence-row {
  display: flex;
  flex-direction: row;
  align-items: center;
  flex-wrap: wrap;
  gap: 4px;
}

.rv-alternation { }
.rv-alternation-col {
  display: flex;
  flex-direction: column;
  gap: 6px;
  padding: 10px 14px;
  border-left: 2px dashed var(--group-color);
  border-right: 2px dashed var(--group-color);
  border-radius: 4px;
}
.rv-or-label {
  color: var(--muted);
  font-size: 11px;
  text-align: center;
  padding: 2px 0;
  letter-spacing: 0.12em;
}

.rv-group {
  padding: 10px 12px;
  border: 1px solid var(--group-color);
  border-radius: 8px;
  background: rgba(197, 163, 255, 0.05);
  display: inline-block;
}
.rv-group-label {
  font-size: 10px;
  color: var(--group-color);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 6px;
  text-align: center;
}

.rv-quantifier {
  display: inline-block;
  padding: 10px 12px;
  border: 1px dashed var(--quantifier-color);
  border-radius: 8px;
  background: rgba(138, 147, 166, 0.05);
}
.rv-quantifier-label {
  font-size: 11px;
  color: var(--quantifier-color);
  text-align: center;
  margin-bottom: 6px;
  font-weight: 600;
}

/* Match highlights -------------------------------------------------- */

.match-output {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 14px 18px;
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 13px;
}
.match-output pre {
  margin: 0;
  white-space: pre-wrap;
  word-break: break-all;
}
.match-output mark {
  background: var(--match-bg);
  color: var(--accent);
  border: 1px solid var(--match-border);
  border-radius: 3px;
  padding: 0 2px;
}
.rv-nomatch {
  color: var(--muted);
  font-style: italic;
  display: block;
  margin-bottom: 8px;
}

footer {
  padding: 24px 32px;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 12px;
  text-align: center;
}

@media (max-width: 700px) {
  header, main, footer { padding-left: 18px; padding-right: 18px; }
  .row { flex-direction: column; align-items: stretch; }
  .flags-field { width: 100%; }
}