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

:root {
  --accent: #2563eb;
  --accent-hover: #1d4ed8;
  --secondary-hover: #16a34a;
  --secondary-hover-border: #15803d;
  --bg: #f5f6f8;
  --card: #ffffff;
  --text: #1c1e21;
  --muted: #6b7280;
  --border: #d9dce1;
  --error-bg: #fdecea;
  --error-text: #b3261e;
}

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

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px 20px 80px;
}

header {
  text-align: center;
  margin-bottom: 28px;
}

h1 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}

.subtitle {
  color: var(--muted);
  margin-top: 4px;
}

.input-section {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  border: 0;
}

#channel-select {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 11px 14px;
  font-size: 0.95rem;
  font-family: inherit;
  background: #fff;
  min-width: 300px;
}

#channel-select:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: transparent;
}

.hint-text {
  color: var(--error-text);
  background: var(--error-bg);
  border-radius: 8px;
  padding: 10px 14px;
  font-size: 0.85rem;
  margin-top: 12px;
}

.hint-text code {
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
}

textarea {
  width: 100%;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 14px;
  font-size: 0.95rem;
  font-family: inherit;
  resize: vertical;
}

textarea:focus {
  outline: 2px solid var(--accent);
  outline-offset: -1px;
  border-color: transparent;
}

.input-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 12px;
  gap: 12px;
  flex-wrap: wrap;
}

#char-counter {
  color: var(--muted);
  font-size: 0.85rem;
}

.footer-actions {
  display: flex;
  align-items: center;
  gap: 14px;
  flex-wrap: wrap;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--muted);
  font-size: 0.9rem;
  cursor: pointer;
  user-select: none;
  white-space: nowrap;
}

.checkbox-label input {
  width: 16px;
  height: 16px;
  accent-color: var(--accent);
  cursor: pointer;
}

button, .button {
  background: var(--accent);
  color: #fff;
  border: none;
  border-radius: 8px;
  padding: 12px 24px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  display: inline-block;
  font-family: inherit;
}

button:hover, .button:hover {
  background: var(--accent-hover);
}

button:disabled {
  background: var(--muted);
  cursor: not-allowed;
}

button.secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}

button.secondary:hover {
  background: var(--secondary-hover);
  border-color: var(--secondary-hover-border);
  color: #fff;
}

.error-banner {
  background: var(--error-bg);
  color: var(--error-text);
  border-radius: 8px;
  padding: 14px 18px;
  margin-top: 16px;
}

.loading {
  text-align: center;
  margin-top: 36px;
  color: var(--muted);
}

.spinner {
  width: 44px;
  height: 44px;
  border: 4px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  margin: 0 auto 14px;
  animation: spin 0.9s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.elapsed-timer {
  margin-top: 8px;
  font-size: 0.85rem;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
}

.result {
  margin-top: 32px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 20px;
}

.result img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: contain;
  border-radius: 8px;
  background: #eee;
}

.result img.preview-checker {
  background: repeating-conic-gradient(#e2e5ea 0% 25%, #ffffff 0% 50%) 0 0 / 24px 24px;
}

.result img.preview-black {
  background: #111;
}

.result img.preview-white {
  background: #fff;
  border: 1px solid var(--border);
}

.preview-switcher {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 12px;
  color: var(--muted);
  font-size: 0.85rem;
}

.preview-switcher .bg-option {
  padding: 6px 12px;
  font-size: 0.85rem;
  font-weight: 500;
  background: transparent;
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 6px;
}

.preview-switcher .bg-option:hover {
  background: var(--bg);
}

.preview-switcher .bg-option.active {
  border-color: var(--accent);
  color: var(--accent);
  background: transparent;
}

#result-warnings.warnings {
  margin: 0 0 12px;
  color: #92400e;
  background: #fef3c7;
}

.result-actions {
  display: flex;
  gap: 12px;
  margin-top: 16px;
}

details {
  margin-top: 16px;
  color: var(--muted);
  font-size: 0.9rem;
}

details pre {
  white-space: pre-wrap;
  background: var(--bg);
  border-radius: 8px;
  padding: 12px;
  margin-top: 8px;
  font-family: inherit;
}

.overlay {
  position: fixed;
  inset: 0;
  background: rgba(28, 30, 33, 0.65);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
}

.gate-card {
  background: var(--card);
  border-radius: 12px;
  padding: 32px;
  width: min(380px, 90vw);
  text-align: center;
}

.gate-card p {
  color: var(--muted);
  margin: 8px 0 16px;
}

.gate-card form {
  display: flex;
  gap: 8px;
}

.gate-card input {
  flex: 1;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 10px 12px;
  font-size: 1rem;
}

.error-text {
  color: var(--error-text);
  font-size: 0.9rem;
  margin-top: 12px;
}

.hidden {
  display: none !important;
}