:root {
  --color-bg: #ffffff;
  --color-surface: #fafafa;
  --color-text: #1a1a1a;
  --color-text-muted: #666666;
  --color-border: #e5e5e5;
  --color-accent: #3b82f6;
  --color-success: #10b981;
  --color-hover: #f0f0f0;

  --font-system:
    -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
    Arial, sans-serif;
  --font-mono: "SF Mono", Monaco, "Courier New", monospace;

  --spacing-xs: 8px;
  --spacing-sm: 12px;
  --spacing-md: 16px;
  --spacing-lg: 20px;
  --spacing-xl: 40px;

  --radius: 8px;
  --transition: 150ms ease;
}

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

body {
  font-family: var(--font-system);
  font-size: 14px;
  line-height: 1.6;
  color: var(--color-text);
  background-color: var(--color-bg);
  overflow-x: hidden;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-lg);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.header {
  text-align: center;
  margin-bottom: var(--spacing-xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 1px solid var(--color-border);
}

.header h1 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

.platform-selector {
  font-family: var(--font-system);
  font-size: 14px;
  padding: var(--spacing-sm) var(--spacing-md);
  padding-right: 36px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-surface);
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath fill='%23666666' d='M6 9L1 4h10z'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 12px center;
  background-size: 12px;
  color: var(--color-text);
  cursor: pointer;
  transition: border-color var(--transition);
  min-width: 200px;
  appearance: none;
  -webkit-appearance: none;
  -moz-appearance: none;
}

.platform-selector:hover {
  border-color: var(--color-accent);
}

.platform-selector:focus {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-color: var(--color-accent);
}

.content {
  flex: 1;
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

@media (min-width: 768px) {
  .content {
    grid-template-columns: 1fr 1fr;
  }
}

.column {
  display: flex;
  flex-direction: column;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--spacing-md);
  min-height: 400px;
}

.column-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-sm);
}

.column-header label {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.clear-btn {
  font-family: var(--font-system);
  font-size: 12px;
  padding: var(--spacing-xs) var(--spacing-sm);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  background-color: var(--color-bg);
  color: var(--color-text-muted);
  cursor: pointer;
  transition: all var(--transition);
}

.clear-btn:hover {
  background-color: var(--color-hover);
  color: var(--color-text);
}

.clear-btn:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.input-textarea {
  flex: 1;
  font-family: var(--font-mono);
  font-size: 14px;
  padding: var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-bg);
  color: var(--color-text);
  resize: vertical;
  min-height: 300px;
  transition: border-color var(--transition);
}

.input-textarea:focus {
  outline: none;
  border-color: var(--color-accent);
}

.input-textarea::placeholder {
  color: var(--color-text-muted);
  opacity: 0.6;
}

.input-footer {
  display: flex;
  justify-content: flex-end;
  margin-top: var(--spacing-sm);
  font-size: 12px;
  color: var(--color-text-muted);
}

.output-preview {
  flex: 1;
  font-family: var(--font-mono);
  font-size: 14px;
  padding: var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background-color: var(--color-bg);
  color: var(--color-text);
  overflow-y: auto;
  white-space: pre-wrap;
  word-wrap: break-word;
  min-height: 300px;
  margin-bottom: var(--spacing-sm);
}

.output-preview:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.copy-btn {
  font-family: var(--font-system);
  font-size: 14px;
  font-weight: 600;
  padding: var(--spacing-sm) var(--spacing-lg);
  border: none;
  border-radius: var(--radius);
  background-color: var(--color-accent);
  color: white;
  cursor: pointer;
  transition: all var(--transition);
  align-self: flex-end;
}

.copy-btn:hover {
  background-color: #2563eb;
  transform: translateY(-1px);
}

.copy-btn:active {
  transform: translateY(0);
}

.copy-btn:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.copy-btn.success {
  background-color: var(--color-success);
}

.footer {
  text-align: center;
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
  margin-top: auto;
}

.shortcuts-hint {
  font-size: 12px;
  color: var(--color-text-muted);
  line-height: 1.8;
}

.shortcuts-hint kbd {
  display: inline-block;
  padding: 2px 6px;
  font-family: var(--font-mono);
  font-size: 11px;
  line-height: 1.4;
  color: var(--color-text);
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 3px;
  box-shadow: 0 1px 0 var(--color-border);
}

@media (max-width: 767px) {
  .container {
    padding: var(--spacing-md);
  }

  .header {
    margin-bottom: var(--spacing-lg);
  }

  .header h1 {
    font-size: 20px;
  }

  .platform-selector {
    width: 100%;
  }

  .shortcuts-hint {
    display: none;
  }

  .column {
    min-height: 300px;
  }
}