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

:root {
  --bg: #0f172a;
  --bg-card: #1e293b;
  --bg-input: #0f172a;
  --border: #334155;
  --border-focus: #3b82f6;
  --text: #e2e8f0;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  --primary: #3b82f6;
  --secondary: #475569;
  --secondary-hover: #64748b;
  --success: #22c55e;
  --error: #ef4444;
  --warning: #f59e0b;
  --diff-added: rgba(34,197,94,0.12);
  --diff-added-border: #22c55e;
  --diff-removed: rgba(239,68,68,0.12);
  --diff-removed-border: #ef4444;
  --diff-changed: rgba(251,191,36,0.12);
  --diff-changed-border: #f59e0b;
  --diff-word-add: rgba(34,197,94,0.35);
  --diff-word-remove: rgba(239,68,68,0.35);
  --radius: 8px;
  --radius-sm: 6px;
  --font-mono: 'SF Mono', 'Fira Code', 'Cascadia Code', 'JetBrains Mono', monospace;
  --font-ui: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
}

html { font-size: 15px; }
body {
  font-family: var(--font-ui);
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.6;
}

.container { max-width: 1200px; margin: 0 auto; padding: 0 20px; }

/* === Header === */
.header {
  border-bottom: 1px solid var(--border);
  padding: 20px 0;
  background: linear-gradient(135deg, #0f172a 0%, #1a2a4a 100%);
}
.header-inner { display: flex; align-items: baseline; gap: 16px; flex-wrap: wrap; }
.logo { font-size: 1.5rem; font-weight: 700; color: var(--text); letter-spacing: -0.5px; }
.tagline { color: var(--text-muted); font-size: 0.9rem; }

/* === View Controls === */
.view-controls {
  display: flex; justify-content: space-between; align-items: center;
  margin-top: 20px; padding: 8px 12px;
  background: var(--bg-card); border-radius: var(--radius) var(--radius) 0 0;
  border: 1px solid var(--border); border-bottom: none;
  flex-wrap: wrap; gap: 8px;
}

.view-tabs { display: flex; gap: 2px; background: var(--bg-input); border-radius: var(--radius-sm); padding: 2px; }
.view-tab {
  padding: 6px 14px; border: none; background: transparent; color: var(--text-muted);
  font-size: 0.82rem; font-family: var(--font-ui); cursor: pointer; border-radius: 4px;
  transition: all 0.15s;
}
.view-tab:hover { color: var(--text); }
.view-tab.active { color: #fff; background: var(--primary); }

.view-actions { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }

.diff-stats {
  font-size: 0.82rem; color: var(--text-muted); padding: 4px 10px;
  background: var(--bg-input); border-radius: var(--radius-sm);
}

/* === Input Section === */
.input-section {
  display: flex; gap: 8px; padding: 12px;
  background: var(--bg-card); border: 1px solid var(--border);
  border-top: none;
}
@media (max-width: 700px) {
  .input-section { flex-direction: column; }
}

.input-panel { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 4px; }
.panel-header {
  display: flex; justify-content: space-between; align-items: center;
}
.panel-header label { font-size: 0.82rem; font-weight: 600; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.5px; }
.line-badge { font-size: 0.72rem; color: var(--text-dim); }

.diff-editor {
  width: 100%; min-height: 200px; padding: 12px;
  background: var(--bg-input); color: var(--text);
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  font-family: var(--font-mono); font-size: 0.82rem; line-height: 1.6;
  resize: vertical; tab-size: 4;
  transition: border-color 0.15s;
}
.diff-editor:focus { outline: none; border-color: var(--border-focus); box-shadow: 0 0 0 2px rgba(59,130,246,0.15); }
.diff-editor::placeholder { color: var(--text-dim); }

/* === Options Bar === */
.options-bar {
  display: flex; gap: 16px; padding: 10px 12px; flex-wrap: wrap;
  background: var(--bg-card); border: 1px solid var(--border); border-top: none;
  border-bottom: none;
}

.checkbox-label {
  display: flex; align-items: center; gap: 6px;
  font-size: 0.82rem; color: var(--text-muted); cursor: pointer;
}
.checkbox-label input { accent-color: var(--primary); }

/* === Diff Output === */
.diff-output {
  display: flex; gap: 8px; padding: 0;
  background: var(--bg-card); border: 1px solid var(--border); border-top: none;
}
.diff-panel { flex: 1; min-width: 0; display: flex; flex-direction: column; }
.diff-panel.unified { flex: none; width: 100%; }

.diff-panel-header {
  padding: 8px 12px; font-size: 0.78rem; font-weight: 600;
  text-transform: uppercase; letter-spacing: 0.5px;
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center; gap: 6px;
}
.removed-header { background: var(--diff-removed); color: var(--error); }
.added-header { background: var(--diff-added); color: var(--success); }

.diff-count {
  font-size: 0.72rem; padding: 1px 6px; border-radius: 8px;
  background: rgba(0,0,0,0.2);
}

.diff-content {
  padding: 0; overflow-x: auto; max-height: 600px; overflow-y: auto;
  font-family: var(--font-mono); font-size: 0.8rem; line-height: 1.5;
}

/* === Diff Lines === */
.diff-line {
  display: flex; min-height: 24px; padding: 0 8px; border-bottom: 1px solid rgba(255,255,255,0.04);
}
.diff-line-num {
  width: 40px; min-width: 40px; padding-right: 8px; text-align: right;
  color: var(--text-dim); font-size: 0.72rem; user-select: none;
  padding-top: 2px;
}
.diff-line-content {
  flex: 1; white-space: pre-wrap; word-break: break-all; padding: 2px 0;
}

.line-unchanged { background: transparent; }
.line-added { background: var(--diff-added); }
.line-removed { background: var(--diff-removed); }
.line-changed-left { background: var(--diff-removed); }
.line-changed-right { background: var(--diff-added); }
.line-context { background: rgba(59,130,246,0.05); color: var(--text-dim); font-style: italic; }

/* === Word-level diff === */
.word-added { background: var(--diff-word-add); border-radius: 2px; padding: 0 1px; }
.word-removed { background: var(--diff-word-remove); border-radius: 2px; padding: 0 1px; }

/* === Unified View === */
.unified .diff-line { padding: 0 8px; }
.unified .diff-line-num { flex: none; }
.unified .line-added .diff-line-num { color: var(--success); }
.unified .line-removed .diff-line-num { color: var(--error); }
.unified .line-changed-left .diff-line-num,
.unified .line-changed-right .diff-line-num { color: var(--warning); }

/* === Summary === */
.diff-summary {
  padding: 12px 16px;
  background: var(--bg-card); border: 1px solid var(--border); border-top: none;
  border-radius: 0 0 var(--radius) var(--radius);
  font-size: 0.85rem; color: var(--text-muted);
  margin-top: 0;
}

/* === Buttons === */
.btn {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 6px 12px; border: none; border-radius: var(--radius-sm);
  font-size: 0.8rem; font-family: var(--font-ui); font-weight: 500;
  cursor: pointer; transition: all 0.15s; white-space: nowrap;
}
.btn-sm { padding: 4px 10px; font-size: 0.78rem; background: var(--secondary); color: #e2e8f0; }
.btn-sm:hover { background: var(--secondary-hover); }

.placeholder-text { color: var(--text-dim); font-style: italic; }

/* === Toast === */
.toast {
  position: fixed; bottom: 24px; left: 50%; transform: translateX(-50%);
  padding: 10px 24px; border-radius: var(--radius); background: var(--bg-card);
  border: 1px solid var(--border); color: var(--text); font-size: 0.85rem;
  box-shadow: 0 4px 20px rgba(0,0,0,0.3); z-index: 100;
  animation: toastIn 0.3s ease;
}
@keyframes toastIn {
  from { opacity: 0; transform: translateX(-50%) translateY(10px); }
  to { opacity: 1; transform: translateX(-50%) translateY(0); }
}

/* === Footer === */
.footer {
  text-align: center; padding: 32px 0; margin-top: 40px;
  border-top: 1px solid var(--border); color: var(--text-dim); font-size: 0.82rem;
}
.footer-small { margin-top: 4px; font-size: 0.75rem; }
/* === SEO / GEO Content === */
.language-switcher { margin-left: auto; display: inline-flex; gap: 4px; padding: 3px; border: 1px solid var(--border); border-radius: var(--radius-xs); background: rgba(15,23,42,0.35); }
.language-switcher a { color: var(--text-muted); text-decoration: none; font-size: 0.76rem; line-height: 1; padding: 6px 8px; border-radius: 5px; }
.language-switcher a:hover, .language-switcher a.active { color: #fff; background: var(--primary); }
.seo-content { margin-top: 28px; display: flex; flex-direction: column; gap: 16px; color: var(--text-muted); }
.seo-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 16px; }
.seo-block { background: rgba(255,255,255,0.03); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 18px; }
.seo-block h2 { color: var(--text); font-size: 1rem; line-height: 1.35; margin: 0 0 10px; letter-spacing: 0; }
.seo-block p { margin: 0; }
.seo-block ul { margin: 0; padding-left: 18px; }
.seo-block li + li { margin-top: 6px; }
.faq-list details { border-top: 1px solid var(--border); padding: 10px 0; }
.faq-list details:first-of-type { border-top: 0; }
.faq-list summary { color: var(--text); cursor: pointer; font-weight: 600; }
.faq-list details p { margin-top: 8px; }
@media (max-width: 720px) { .language-switcher { margin-left: 0; } .seo-grid { grid-template-columns: 1fr; } }
.related-links { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
.related-links a { color: var(--text); text-decoration: none; border: 1px solid var(--border); border-radius: var(--radius-xs); padding: 7px 10px; background: rgba(255,255,255,0.04); }
.related-links a:hover { border-color: var(--primary); color: #fff; }