/* ===== CSS Variables ===== */
:root {
  --color-bg: #f3f4f6;
  --color-surface: #ffffff;
  --color-text: #111827;
  --color-text-secondary: #4b5563;
  --color-accent: #2563eb;
  --color-accent-light: #eff6ff;
  --color-brand: #dc2626;
  --color-border: #d1d5db;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-card: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
  --shadow-card-hover: 0 10px 24px rgba(0, 0, 0, 0.15);
  --radius: 10px;
  --radius-sm: 6px;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Hiragino Sans', sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', Consolas, monospace;
  --transition: 0.15s ease;
}

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

/* ===== Base ===== */
html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Layout ===== */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 0 24px;
}

.container--narrow {
  max-width: 960px;
}

/* ===== Header ===== */
.header {
  background-color: var(--color-surface);
  padding: 16px 0;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
  border-top: 3px solid var(--color-brand);
}

.header__inner {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header__title {
  font-size: 1.125rem;
  font-weight: 600;
  color: var(--color-text);
  text-decoration: none;
  letter-spacing: -0.02em;
}

/* ===== Language Switcher ===== */
.lang-switch {
  display: flex;
  gap: 2px;
  background-color: var(--color-bg);
  padding: 3px;
  border-radius: 8px;
}

.lang-switch__btn {
  padding: 6px 12px;
  border: none;
  background: transparent;
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  border-radius: 6px;
  transition: all var(--transition);
}

.lang-switch__btn:hover {
  color: var(--color-text);
}

.lang-switch__btn.active {
  background-color: var(--color-surface);
  color: var(--color-text);
  box-shadow: var(--shadow-sm);
}

/* ===== Main Content ===== */
.main {
  padding: 56px 0;
}

.page-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.03em;
  margin-bottom: 8px;
  color: var(--color-text);
}

.page-description {
  color: var(--color-text-secondary);
  font-size: 1rem;
  margin-bottom: 40px;
}

/* ===== Category Grid ===== */
.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

/* ===== Category Card ===== */
.category-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: all var(--transition);
}

.category-card:hover {
  box-shadow: var(--shadow-card-hover);
  border-color: var(--color-accent);
}

.category-header {
  background: linear-gradient(135deg, var(--color-accent) 0%, #1d4ed8 100%);
  padding: 14px 18px;
}

.category-title {
  font-size: 0.8125rem;
  font-weight: 600;
  color: #fff;
  margin: 0;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ===== Tool List ===== */
.tool-list {
  padding: 8px 0;
}

.tool-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 18px;
  text-decoration: none;
  color: var(--color-text);
  font-size: 0.875rem;
  transition: all var(--transition);
  border-left: 3px solid transparent;
}

.tool-link:hover {
  background-color: var(--color-accent-light);
  border-left-color: var(--color-accent);
  color: var(--color-accent);
}

.tool-link__number {
  font-size: 0.6875rem;
  color: var(--color-text-secondary);
  font-family: var(--font-mono);
  background: var(--color-bg);
  padding: 2px 6px;
  border-radius: 4px;
  min-width: 32px;
  text-align: center;
}

.tool-link:hover .tool-link__number {
  background: var(--color-accent);
  color: #fff;
}

/* ===== Card Grid (legacy) ===== */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 14px;
}

/* ===== Card ===== */
.card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 18px;
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow-card);
  transition: all var(--transition);
  display: block;
}

.card:hover {
  border-color: var(--color-accent);
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-2px);
}

.card__number {
  display: inline-block;
  font-size: 0.6875rem;
  font-weight: 600;
  color: var(--color-accent);
  background-color: var(--color-accent-light);
  padding: 4px 8px;
  border-radius: 6px;
  margin-bottom: 14px;
  letter-spacing: 0.02em;
}

.card__title {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 6px;
  letter-spacing: -0.01em;
}

.card__description {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  line-height: 1.5;
}

/* ===== Stats Grid ===== */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 20px;
}

.stat-card {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 20px 16px;
  text-align: center;
}

.stat-card__value {
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--color-text);
  font-family: var(--font-mono);
  letter-spacing: -0.02em;
}

.stat-card__label {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  margin-top: 4px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* ===== Textarea ===== */
.textarea-wrapper {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}

.textarea-wrapper:focus-within {
  border-color: var(--color-accent);
}

.textarea {
  width: 100%;
  min-height: 280px;
  padding: 20px;
  border: none;
  outline: none;
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  line-height: 1.7;
  resize: vertical;
  background: transparent;
  color: var(--color-text);
}

.textarea::placeholder {
  color: var(--color-text-secondary);
  opacity: 0.7;
}

/* ===== Textarea Header ===== */
.textarea-header {
  display: flex;
  justify-content: flex-end;
  padding: 10px 16px;
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

.clear-btn {
  padding: 6px 12px;
  border: none;
  background: var(--color-surface);
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  border-radius: 6px;
  transition: all var(--transition);
}

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

/* ===== Back Link ===== */
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 500;
  margin-bottom: 28px;
  transition: color var(--transition);
}

.back-link:hover {
  color: var(--color-accent);
}

.back-link svg {
  width: 14px;
  height: 14px;
}

/* ===== Footer ===== */
.footer {
  padding: 32px 0;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .container {
    padding: 0 16px;
  }

  .main {
    padding: 40px 0;
  }

  .page-title {
    font-size: 1.5rem;
  }

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .stat-card__value {
    font-size: 1.5rem;
  }

  .card-grid {
    grid-template-columns: 1fr;
  }
}