:root {
  --bg: #ffffff;
  --bg-secondary: #f5f7fa;
  --bg-card: #ffffff;
  --text: #303133;
  --text-secondary: #606266;
  --text-muted: #909399;
  --border: #dcdfe6;
  --border-light: #e4e7ed;
  --primary: #67c23a;
  --primary-light: #95d475;
  --primary-dark: #529b2e;
  --danger: #f56c6c;
  --warning: #e6a23c;
  --info: #909399;
  --success: #67c23a;
  --shadow: 0 2px 12px 0 rgba(0,0,0,0.1);
  --radius: 8px;
  --header-height: 60px;
  --sidebar-width: 200px;
  --sidebar-collapsed: 64px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

.dark {
  --bg: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-card: #1e2a4a;
  --text: #e5eaf3;
  --text-secondary: #a3a6ad;
  --text-muted: #6c6e72;
  --border: #4c4d4f;
  --border-light: #363637;
  --shadow: 0 2px 12px 0 rgba(0,0,0,0.3);
}

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

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  transition: background 0.3s, color 0.3s;
  overflow: hidden;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-light); }

/* ===== HEADER ===== */
.header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  height: var(--header-height);
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  display: flex; align-items: center;
  padding: 0 16px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
}
.header-logo {
  display: flex; align-items: center; gap: 8px;
  font-size: 18px; font-weight: 700; color: var(--text);
  text-decoration: none;
  min-width: var(--sidebar-width);
}
.header-logo img { width: 28px; height: 28px; }
.header-actions {
  display: flex; align-items: center; gap: 8px;
  margin-left: auto;
}
.header-btn {
  background: none; border: none; cursor: pointer;
  width: 36px; height: 36px; border-radius: 8px;
  display: flex; align-items: center; justify-content: center;
  color: var(--text); font-size: 18px;
  transition: background 0.2s;
}
.header-btn:hover { background: var(--bg-secondary); }
.header-btn svg { width: 20px; height: 20px; }

/* ===== SIDEBAR ===== */
.sidebar {
  position: fixed; top: var(--header-height); left: 0; bottom: 0;
  width: var(--sidebar-width);
  background: var(--bg);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  transition: transform 0.3s, width 0.3s;
  z-index: 999;
  padding: 8px 0;
}
.sidebar.collapsed { width: var(--sidebar-collapsed); }
.sidebar-title {
  padding: 12px 16px 4px;
  font-size: 11px; text-transform: uppercase;
  color: var(--text-muted); letter-spacing: 1px;
  white-space: nowrap; overflow: hidden;
}
.sidebar.collapsed .sidebar-title { padding: 12px 8px 4px; font-size: 9px; }
.sidebar-item {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 16px; color: var(--text);
  text-decoration: none; font-size: 14px;
  transition: background 0.2s; border-radius: 0;
  white-space: nowrap; overflow: hidden;
}
.sidebar-item:hover { background: var(--bg-secondary); }
.sidebar-item.active { color: var(--primary); background: rgba(103,194,58,0.1); }
.sidebar-item svg { width: 18px; height: 18px; flex-shrink: 0; }
.sidebar-item span { overflow: hidden; text-overflow: ellipsis; }
.collapsed .sidebar-item span { display: none; }
.collapsed .sidebar-item { justify-content: center; padding: 12px 0; }

/* ===== MAIN CONTENT ===== */
.main {
  position: fixed; top: var(--header-height); left: var(--sidebar-width);
  right: 0; bottom: 0; overflow-y: auto; padding: 24px;
  transition: left 0.3s;
}
.main.expanded { left: var(--sidebar-collapsed); }

/* ===== MOBILE OVERLAY ===== */
.sidebar-mask {
  display: none; position: fixed; inset: 0;
  background: rgba(0,0,0,0.5); z-index: 998;
}

/* ===== PAGE COMMON ===== */
.page-header { margin-bottom: 20px; }
.page-title { font-size: 24px; font-weight: 600; }
.breadcrumb { display: flex; gap: 6px; align-items: center; font-size: 13px; color: var(--text-muted); margin-bottom: 12px; }
.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--primary); }
.breadcrumb span { color: var(--text); }
.breadcrumb-sep { color: var(--text-muted); }

/* ===== CARD ===== */
.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); margin-bottom: 16px;
  box-shadow: var(--shadow);
}
.card-header {
  padding: 14px 20px; border-bottom: 1px solid var(--border);
  font-weight: 600; font-size: 15px;
  display: flex; align-items: center; gap: 6px;
}
.card-body { padding: 20px; }

/* Info card */
.info-card { border-left: 3px solid var(--primary); }
.info-card .card-body { font-size: 13px; line-height: 2; color: var(--text-secondary); }
.info-card .note-text { color: var(--info); }
.info-card .warning-text { color: var(--danger); }

/* ===== BUTTONS ===== */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  padding: 8px 16px; border-radius: 6px; font-size: 14px; cursor: pointer;
  border: 1px solid var(--border); background: #fff; color: var(--text);
  transition: all 0.2s; font-family: inherit; white-space: nowrap;
}
.btn:hover { border-color: var(--primary); color: var(--primary); }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.btn-primary { background: var(--primary); border-color: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); border-color: var(--primary-dark); color: #fff; }
.btn-success { background: var(--success); border-color: var(--success); color: #fff; }
.btn-success:hover { background: #529b2e; color: #fff; }
.btn-danger { background: var(--danger); border-color: var(--danger); color: #fff; }
.btn-danger:hover { background: #e04545; color: #fff; }
.btn-warning { background: var(--warning); border-color: var(--warning); color: #fff; }
.btn-sm { padding: 5px 12px; font-size: 12px; }
.btn-lg { padding: 12px 40px; font-size: 16px; }

/* ===== FORM CONTROLS ===== */
.form-group { margin-bottom: 14px; }
.form-label { display: block; font-size: 13px; font-weight: 500; margin-bottom: 4px; color: var(--text); }
.form-input, .form-select, .form-textarea {
  width: 100%; padding: 8px 12px; border: 1px solid var(--border);
  border-radius: 6px; font-size: 14px; background: var(--bg);
  color: var(--text); font-family: inherit; transition: border-color 0.2s;
}
.form-input:focus, .form-select:focus, .form-textarea:focus {
  outline: none; border-color: var(--primary);
}
.form-textarea { resize: vertical; min-height: 100px; }
.form-hint { font-size: 12px; color: var(--text-muted); margin-top: 4px; }
.form-inline { display: flex; gap: 12px; align-items: center; flex-wrap: wrap; }
.form-inline .form-group { margin-bottom: 0; }

/* ===== COLOR PICKER ===== */
.form-color { width: 40px; height: 32px; border: 1px solid var(--border); border-radius: 4px; cursor: pointer; padding: 2px; }

/* ===== SLIDER ===== */
.form-range { width: 100%; accent-color: var(--primary); }

/* ===== RADIO / CHECKBOX GROUP ===== */
.radio-group { display: flex; gap: 12px; flex-wrap: wrap; }
.radio-item { display: flex; align-items: center; gap: 6px; cursor: pointer; font-size: 14px; }
.radio-item input { accent-color: var(--primary); }

/* ===== TABS ===== */
.tabs { display: flex; border-bottom: 2px solid var(--border); margin-bottom: 16px; }
.tab {
  padding: 10px 20px; cursor: pointer; border: none; background: none;
  font-size: 14px; color: var(--text-secondary); border-bottom: 2px solid transparent;
  margin-bottom: -2px; transition: all 0.2s;
}
.tab.active { color: var(--primary); border-bottom-color: var(--primary); }
.tab:hover { color: var(--primary); }

/* ===== TABLE ===== */
.table-wrap { overflow-x: auto; }
.table { width: 100%; border-collapse: collapse; font-size: 14px; }
.table th, .table td { padding: 10px 14px; text-align: left; border: 1px solid var(--border); }
.table th { background: var(--bg-secondary); font-weight: 600; white-space: nowrap; }
.table tr:hover td { background: var(--bg-secondary); }

/* ===== TAG ===== */
.tag {
  display: inline-block; padding: 2px 8px; border-radius: 4px;
  font-size: 12px; font-weight: 500;
}
.tag-success { background: rgba(103,194,58,0.1); color: var(--success); }
.tag-warning { background: rgba(230,162,60,0.1); color: var(--warning); }
.tag-danger { background: rgba(245,108,108,0.1); color: var(--danger); }
.tag-info { background: rgba(144,147,153,0.1); color: var(--info); }

/* ===== PROGRESS ===== */
.progress { height: 6px; background: var(--bg-secondary); border-radius: 3px; overflow: hidden; }
.progress-bar { height: 100%; background: var(--primary); border-radius: 3px; transition: width 0.3s; }
.progress-bar.danger { background: var(--danger); }

/* ===== UPLOAD ZONE ===== */
.upload-zone {
  border: 2px dashed var(--border); border-radius: var(--radius);
  padding: 40px 20px; text-align: center; cursor: pointer;
  transition: border-color 0.2s; background: var(--bg-secondary);
}
.upload-zone:hover { border-color: var(--primary); }
.upload-zone svg { width: 48px; height: 48px; color: var(--text-muted); margin-bottom: 12px; }
.upload-zone .upload-text { font-size: 14px; color: var(--text-secondary); }
.upload-zone .upload-hint { font-size: 12px; color: var(--text-muted); margin-top: 6px; }
.upload-zone em { color: var(--primary); font-style: normal; }

/* ===== TOOL GRID (for index pages) ===== */
.tool-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
}
.tool-card {
  display: flex; align-items: center; gap: 14px;
  padding: 18px; background: var(--bg-card);
  border: 1px solid var(--border); border-radius: var(--radius);
  text-decoration: none; color: var(--text);
  transition: all 0.2s;
}
.tool-card:hover { border-color: var(--primary); box-shadow: var(--shadow); transform: translateY(-2px); }
.tool-card-icon {
  width: 44px; height: 44px; border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  background: rgba(103,194,58,0.1); color: var(--primary); flex-shrink: 0;
}
.tool-card-icon svg { width: 22px; height: 22px; }
.tool-card-info { overflow: hidden; }
.tool-card-title { font-size: 14px; font-weight: 600; }
.tool-card-desc { font-size: 12px; color: var(--text-muted); margin-top: 2px; }

/* ===== RECOMMENDED TOOLS (bottom) ===== */
.recommended { margin-top: 24px; }
.recommended-title { font-size: 16px; font-weight: 600; margin-bottom: 12px; }
.recommended-grid { display: flex; gap: 12px; flex-wrap: wrap; }
.recommended-item {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 8px 16px; background: var(--bg-secondary);
  border: 1px solid var(--border); border-radius: 20px;
  text-decoration: none; color: var(--text-secondary); font-size: 13px;
  transition: all 0.2s;
}
.recommended-item:hover { border-color: var(--primary); color: var(--primary); }

/* ===== FAQ (home page) ===== */
.faq-section { width: 75%; margin: 35px auto 0; }
.faq-item { border: 1px solid var(--border); border-radius: var(--radius); margin-bottom: 8px; overflow: hidden; }
.faq-question {
  padding: 14px 18px; cursor: pointer; font-weight: 500;
  display: flex; justify-content: space-between; align-items: center;
  background: var(--bg-card);
}
.faq-answer { padding: 0 18px 14px; font-size: 14px; color: var(--text-secondary); display: none; }
.faq-item.open .faq-answer { display: block; }

/* ===== DIALOG / MODAL ===== */
.modal-overlay {
  display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.5);
  z-index: 2000; align-items: center; justify-content: center;
}
.modal-overlay.show { display: flex; }
.modal {
  background: var(--bg-card); border-radius: var(--radius);
  max-width: 480px; width: 90%; padding: 24px;
  box-shadow: 0 8px 40px rgba(0,0,0,0.2);
}
.modal-title { font-size: 16px; font-weight: 600; margin-bottom: 16px; }
.modal-actions { display: flex; justify-content: flex-end; gap: 10px; margin-top: 20px; }

/* ===== TOAST ===== */
.toast {
  position: fixed; top: 20px; left: 50%; transform: translateX(-50%);
  padding: 10px 20px; border-radius: 6px; color: #fff; font-size: 14px;
  z-index: 3000; opacity: 0; transition: opacity 0.3s; pointer-events: none;
}
.toast.show { opacity: 1; }
.toast-success { background: var(--success); }
.toast-error { background: var(--danger); }
.toast-info { background: var(--info); }
.toast-warning { background: var(--warning); }

/* ===== VIDEO/AUDIO PLAYER ===== */
.media-preview { width: 100%; max-height: 200px; border-radius: 8px; background: #000; }

/* ===== COMPARISON LAYOUT ===== */
.compare-row { display: flex; gap: 16px; }
.compare-col { flex: 1; min-width: 0; }
.compare-label { font-weight: 600; margin-bottom: 8px; }
.compare-textarea { width: 100%; min-height: 200px; }

/* ===== DIFF HIGHLIGHT ===== */
.diff-add { background: rgba(103,194,58,0.2); }
.diff-remove { background: rgba(245,108,108,0.2); }
.diff-equal { color: var(--text-muted); }

/* ===== DESIGN TOOLS ===== */
.color-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(80px, 1fr)); gap: 8px; }
.color-swatch { height: 60px; border-radius: 6px; cursor: pointer; border: 1px solid var(--border); transition: transform 0.2s; }
.color-swatch:hover { transform: scale(1.05); }
.color-swatch-name { font-size: 10px; text-align: center; margin-top: 4px; color: var(--text-muted); }

/* ===== COUNTDOWN / STOPWATCH ===== */
.timer-display {
  font-size: 64px; font-weight: 700; text-align: center;
  font-variant-numeric: tabular-nums; letter-spacing: 4px;
  margin: 20px 0;
}
.timer-controls { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; margin: 16px 0; }

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.mobile-show { transform: translateX(0); box-shadow: 2px 0 8px rgba(0,0,0,0.15); }
  .sidebar-mask.show { display: block; }
  .main { left: 0 !important; }
  .header-logo { min-width: 120px; }
  .faq-section { width: 95%; }
  .tool-grid { grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); }
  .compare-row { flex-direction: column; }
  .timer-display { font-size: 40px; }
}

@media (max-width: 480px) {
  .main { padding: 12px; }
  .card-body { padding: 12px; }
  .tool-grid { grid-template-columns: 1fr; }
  .page-title { font-size: 20px; }
  .btn-lg { padding: 10px 24px; font-size: 14px; }
  .timer-display { font-size: 32px; }
}