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

:root {
  --bg: #fafafa;
  --surface: #fff;
  --border: #ddd;
  --text: #222;
  --text-muted: #666;
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --danger: #dc2626;
  --danger-hover: #b91c1c;
  --success: #16a34a;
  --warning: #ca8a04;
  --font-mono: "SF Mono", "Cascadia Code", "Fira Code", "Consolas", monospace;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, sans-serif;
  --radius: 6px;
}

body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  padding: 1.5rem;
  max-width: 720px;
  margin: 0 auto;
}

header {
  margin-bottom: 1.5rem;
}

h1 {
  font-size: 1.5rem;
  font-weight: 700;
}

.subtitle {
  color: var(--text-muted);
  font-size: 0.875rem;
}

.subtitle a {
  color: var(--accent);
  text-decoration: none;
}

.subtitle a:hover {
  text-decoration: underline;
}

h2 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

section {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem;
  margin-bottom: 1rem;
}

/* Connection controls */
.control-row {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
}

.control-row label {
  font-size: 0.875rem;
  font-weight: 500;
  white-space: nowrap;
}

.control-row select {
  flex: 1;
  padding: 0.375rem 0.5rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-family: var(--font-sans);
  background: var(--surface);
}

.button-row {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.75rem;
}

button {
  padding: 0.5rem 1rem;
  border: none;
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-family: var(--font-sans);
  font-weight: 500;
  cursor: pointer;
  transition: background-color 0.15s;
}

button:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

#connect-btn {
  background: var(--accent);
  color: white;
}

#connect-btn:hover:not(:disabled) {
  background: var(--accent-hover);
}

#disconnect-btn {
  background: var(--danger);
  color: white;
}

#disconnect-btn:hover:not(:disabled) {
  background: var(--danger-hover);
}

#clear-log-btn,
#send-btn {
  background: var(--accent);
  color: white;
}

#clear-log-btn:hover:not(:disabled),
#send-btn:hover:not(:disabled) {
  background: var(--accent-hover);
}

/* Status bar */
#status-bar {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.8125rem;
  color: var(--text-muted);
}

#state-indicator {
  font-weight: 600;
}

.state-closed { color: var(--text-muted); }
.state-opening { color: var(--warning); }
.state-open { color: var(--success); }
.state-closing { color: var(--warning); }

/* Browser warning */
#browser-warning {
  margin-top: 0.75rem;
  padding: 0.75rem;
  background: #fef2f2;
  border: 1px solid #fecaca;
  border-radius: var(--radius);
  color: var(--danger);
  font-size: 0.875rem;
}

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

.section-header h2 {
  margin-bottom: 0;
}

.section-controls {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.8125rem;
}

.section-controls label {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  color: var(--text-muted);
  cursor: pointer;
}

#serial-log {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  line-height: 1.6;
  background: #111;
  color: #e5e5e5;
  padding: 0.75rem;
  border-radius: var(--radius);
  height: 280px;
  overflow-y: auto;
  white-space: pre-wrap;
  word-break: break-all;
}

#line-count {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-align: right;
  margin-top: 0.25rem;
}

/* Send controls */
.send-row {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 0.375rem;
}

#send-input {
  flex: 1;
  padding: 0.5rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 0.875rem;
  font-family: var(--font-mono);
}

#send-input:disabled {
  opacity: 0.5;
}

.small-label {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  font-size: 0.8125rem;
  color: var(--text-muted);
  cursor: pointer;
}

/* Error section */
#error-section {
  border-color: #fecaca;
}

#error-section h2 {
  color: var(--danger);
}

#error-log {
  font-family: var(--font-mono);
  font-size: 0.8125rem;
  line-height: 1.6;
  color: var(--danger);
  white-space: pre-wrap;
  word-break: break-all;
}