:root {
  --bg: #f7f7f5;
  --panel-bg: #ffffff;
  --text: #1f2320;
  --muted: #6b7168;
  --border: #dcdfd8;
  --accent: #2f6b4f;
  --accent-hover: #24543e;
  --accent-contrast: #ffffff;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
}

.site-header {
  padding: 2rem 1.5rem 1rem;
  text-align: center;
}

.site-header h1 {
  margin: 0;
  font-size: 2rem;
  letter-spacing: -0.02em;
}

.site-header .plus {
  color: var(--accent);
}

.tagline {
  color: var(--muted);
  margin: 0.3rem 0 0;
}

main {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 1.5rem 3rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.panel {
  background: var(--panel-bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 1.5rem;
}

.panel h2 {
  margin-top: 0;
  font-size: 1.1rem;
}

.hint {
  color: var(--muted);
  font-size: 0.88rem;
  margin: 0.25rem 0 0.75rem;
}

textarea {
  width: 100%;
  font-family: var(--mono);
  font-size: 0.92rem;
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  resize: vertical;
  background: var(--bg);
  color: var(--text);
}

.ref-stats, .run-stats {
  margin-top: 0.5rem;
  font-size: 0.85rem;
  color: var(--muted);
}

.param-group {
  margin-bottom: 1.25rem;
}

.random-seq-group {
  margin-top: 1rem;
  margin-bottom: 0;
}

.random-seq-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.75rem;
}

#random-seq-btn {
  border: 1px solid var(--border);
  background: var(--panel-bg);
  color: var(--text);
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  cursor: pointer;
  font-size: 0.9rem;
}

#random-seq-btn:hover {
  border-color: var(--accent);
}

.param-group > label:first-child {
  display: block;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

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

.button-group button {
  border: 1px solid var(--border);
  background: var(--panel-bg);
  color: var(--text);
  padding: 0.45rem 0.9rem;
  border-radius: 999px;
  cursor: pointer;
  font-size: 0.9rem;
}

.button-group button:hover {
  border-color: var(--accent);
}

.button-group button.active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-contrast);
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  cursor: pointer;
}

.checkbox-label input {
  width: 1.05rem;
  height: 1.05rem;
}

.primary-btn {
  width: 100%;
  padding: 0.8rem;
  border: none;
  border-radius: 8px;
  background: var(--accent);
  color: var(--accent-contrast);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  margin-top: 0.5rem;
}

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

.output-actions {
  display: flex;
  gap: 0.75rem;
  margin-top: 0.75rem;
}

.output-actions button {
  padding: 0.6rem 1.1rem;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--panel-bg);
  cursor: pointer;
  font-size: 0.9rem;
}

.output-actions button:hover {
  border-color: var(--accent);
}

.copy-status {
  min-height: 1.2em;
  font-size: 0.85rem;
  color: var(--accent);
  margin: 0.4rem 0 0;
}

.site-footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.82rem;
  padding: 1.5rem;
}