:root {
  color-scheme: light dark;
  --bg: #0f1419;
  --surface: #1a2332;
  --panel-inset: #121820;
  --border: #2f3b4d;
  --text: #e7ecf3;
  --muted: #8b9bb4;
  --accent: #1d9bf0;
  --accent-hover: #1a8cd8;
  --warn: #f7b955;
  --ok: #00ba7c;
  --danger: #f4212e;
  --radius: 12px;
  --font: system-ui, -apple-system, "Segoe UI", "Hiragino Sans", "Noto Sans JP", sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --container-max: 40rem;
  --page-pad-x: 1rem;
  --page-pad-y: 2rem;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f4f7fb;
    --surface: #ffffff;
    --panel-inset: #eef2f7;
    --border: #d0d7e2;
    --text: #0f1419;
    --muted: #5b6b82;
    --accent: #1a8cd8;
    --accent-hover: #1577b8;
    --warn: #b86a00;
    --ok: #008f5f;
    --danger: #d10f1a;
  }
}

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

html {
  color-scheme: light dark;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  min-height: 100dvh;
  font-family: var(--font);
  font-size: clamp(0.95rem, 0.9rem + 0.25vw, 1.05rem);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  overflow-x: hidden;
}

.container {
  width: min(100% - (var(--page-pad-x) * 2), var(--container-max));
  margin: 0 auto;
  padding: var(--page-pad-y) 0 calc(var(--page-pad-y) + env(safe-area-inset-bottom, 0px));
}

.brand {
  margin: 0 0 0.65rem;
  font-size: clamp(0.75rem, 0.7rem + 0.2vw, 0.85rem);
  font-weight: 600;
  letter-spacing: 0.04em;
}

.home-link {
  color: var(--accent);
  text-decoration: none;
}

.home-link:hover,
.home-link:focus-visible {
  text-decoration: underline;
  outline: none;
}

.footer-nav {
  margin: 0 0 0.75rem;
}

.header h1 {
  margin: 0 0 0.35rem;
  font-size: clamp(1.3rem, 1.1rem + 1vw, 1.9rem);
  font-weight: 700;
  letter-spacing: 0.02em;
  line-height: 1.25;
}

.subtitle {
  margin: 0;
  color: var(--muted);
  font-size: clamp(0.9rem, 0.85rem + 0.25vw, 1rem);
}

.steps {
  margin: 1.5rem 0;
  padding: 1rem 1rem 1rem 2rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  color: var(--muted);
  font-size: clamp(0.85rem, 0.8rem + 0.2vw, 0.95rem);
}

.steps li + li {
  margin-top: 0.35rem;
}

.steps strong {
  color: var(--text);
}

.panel {
  margin-top: 1.25rem;
}

.panel label,
.panel h2 {
  display: block;
  margin: 0 0 0.5rem;
  font-size: clamp(0.8rem, 0.75rem + 0.15vw, 0.9rem);
  font-weight: 600;
  color: var(--muted);
  letter-spacing: 0.04em;
}

textarea {
  display: block;
  width: 100%;
  max-width: 100%;
  padding: 0.85rem 1rem;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: var(--surface);
  color: var(--text);
  font-family: inherit;
  font-size: clamp(1rem, 0.95rem + 0.2vw, 1.1rem);
  line-height: 1.5;
  resize: vertical;
  outline: none;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

textarea:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 28%, transparent);
}

textarea[readonly] {
  color: var(--muted);
  cursor: default;
  background: var(--panel-inset);
}

.hint {
  margin: 0.5rem 0 0;
  font-size: clamp(0.75rem, 0.7rem + 0.15vw, 0.85rem);
  color: var(--muted);
}

.hint.warn {
  color: var(--warn);
}

.hint.mono {
  font-family: var(--mono);
  font-size: clamp(0.7rem, 0.65rem + 0.15vw, 0.8rem);
  word-break: break-all;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin-top: 1rem;
}

.btn {
  appearance: none;
  border: 1px solid var(--border);
  border-radius: 999px;
  min-height: 44px;
  padding: 0.7rem 1.35rem;
  background: var(--surface);
  color: var(--text);
  font: inherit;
  font-size: clamp(0.9rem, 0.85rem + 0.2vw, 1rem);
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, opacity 0.15s ease, box-shadow 0.15s ease;
}

.btn:hover:not(:disabled) {
  border-color: var(--accent);
}

.btn:focus-visible {
  outline: none;
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 35%, transparent);
}

.btn:disabled {
  opacity: 0.45;
  cursor: not-allowed;
}

.btn.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn.primary:hover:not(:disabled) {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
}

.btn.ghost {
  background: transparent;
}

.preview {
  min-height: 3.5rem;
  padding: 0.9rem 1rem;
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  background: var(--panel-inset);
  white-space: pre-wrap;
  word-break: break-word;
  font-size: clamp(1.05rem, 1rem + 0.3vw, 1.2rem);
  line-height: 1.45;
  color: var(--text);
}

.preview.empty {
  color: var(--muted);
  font-size: clamp(0.9rem, 0.85rem + 0.2vw, 1rem);
}

.status {
  min-height: 1.4em;
  margin: 0.5rem 0 0;
  font-size: clamp(0.85rem, 0.8rem + 0.15vw, 0.95rem);
  color: var(--ok);
  font-weight: 600;
}

.status.error {
  color: var(--danger);
}

.footer {
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  font-size: clamp(0.75rem, 0.7rem + 0.2vw, 0.85rem);
  color: var(--muted);
}

.footer code {
  font-family: var(--mono);
  font-size: 0.85em;
}

@media (max-width: 480px) {
  :root {
    --page-pad-x: 0.75rem;
    --page-pad-y: 1.25rem;
  }

  .steps {
    padding: 0.9rem 0.9rem 0.9rem 1.75rem;
  }

  .actions {
    gap: 0.5rem;
  }

  .btn {
    flex: 1 1 calc(50% - 0.5rem);
    text-align: center;
  }

  .btn.ghost {
    flex: 1 1 100%;
  }
}

@media (min-width: 768px) {
  :root {
    --container-max: 44rem;
    --page-pad-x: 1.25rem;
    --page-pad-y: 2.5rem;
  }

  .actions {
    gap: 0.75rem;
  }
}

@media (min-width: 1024px) {
  :root {
    --container-max: 46rem;
  }
}