:root {
  color-scheme: light dark;
  --bg: #f4f6f8;
  --surface: #ffffff;
  --text: #111827;
  --muted: #4b5563;
  --border: #d1d5db;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-text: #ffffff;
  --danger: #b91c1c;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0b1220;
    --surface: #111827;
    --text: #f3f4f6;
    --muted: #9ca3af;
    --border: #374151;
    --primary: #3b82f6;
    --primary-hover: #60a5fa;
    --primary-text: #ffffff;
    --danger: #f87171;
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100dvh;
  font-family: "Segoe UI", "Hiragino Sans", "Yu Gothic UI", "Meiryo", sans-serif;
  background: var(--bg);
  color: var(--text);
}

.container {
  width: min(900px, 100% - 2rem);
  margin: 2rem auto;
  padding: 1.2rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 12px;
}

.header h1 {
  margin: 0;
  font-size: clamp(1.35rem, 2vw, 1.8rem);
}

.header p {
  margin: 0.4rem 0 0;
  color: var(--muted);
  font-size: 0.95rem;
}

.panel {
  margin-top: 1rem;
}

.panel-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem;
}

h2 {
  margin: 0;
  font-size: 1rem;
}

.panel-body {
  display: flex;
  flex-direction: column;
}

textarea {
  width: 100%;
  margin-top: 0.45rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem;
  color: var(--text);
  background: var(--surface);
  font: 400 0.94rem/1.55 Consolas, "BIZ UD Gothic", monospace;
  resize: vertical;
}

textarea::placeholder {
  color: var(--muted);
  font-weight: 600;
}

textarea:focus {
  outline: 2px solid color-mix(in srgb, var(--primary) 40%, transparent 60%);
  border-color: var(--primary);
}

.panel-tools {
  display: flex;
  justify-content: flex-end;
  gap: 0.45rem;
  margin-top: 0.55rem;
}

.convert-center {
  display: flex;
  justify-content: center;
  margin-top: 1rem;
}

.convert-center #convertBtn {
  width: min(460px, 100%);
}

.actions {
  display: flex;
  gap: 0.4rem;
}

.actions-main {
  margin-top: 1rem;
  justify-content: flex-end;
}

button {
  border: 1px solid var(--primary);
  background: var(--primary);
  color: var(--primary-text);
  border-radius: 8px;
  padding: 0.5rem 0.78rem;
  font-weight: 700;
  cursor: pointer;
}

button:hover {
  background: var(--primary-hover);
  border-color: var(--primary-hover);
}

button:focus-visible,
a:focus-visible {
  outline: 2px solid color-mix(in srgb, var(--primary) 72%, transparent 28%);
  outline-offset: 2px;
}

button.secondary {
  border-color: var(--border);
  background: var(--surface);
  color: var(--text);
}

button.secondary:hover {
  background: color-mix(in srgb, var(--surface) 88%, var(--text) 12%);
  border-color: var(--muted);
}

.status {
  min-height: 1.5rem;
  margin: 0.9rem 0 0;
  color: var(--muted);
  font-size: 0.9rem;
}

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

.footer-links {
  margin-top: 1rem;
  display: flex;
  gap: 1rem;
}

.footer-links a {
  color: var(--primary);
}

@media (max-width: 640px) {
  .container {
    width: min(900px, 100% - 1rem);
    margin: 0.9rem auto;
    padding: 0.9rem;
  }

  .panel-head {
    align-items: flex-start;
    flex-direction: column;
  }

  .panel-tools,
  .actions {
    width: 100%;
  }

  .panel-tools button,
  .actions button {
    flex: 1;
  }
}