/* ==========================================================================
   DevTools Hub - CSS Design System & Layout
   ========================================================================== */

/* Google Fonts Import */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@300;400;500;600;700;800&display=swap');

/* CSS Custom Properties / Color Tokens */
:root {
  /* Common variables */
  --font-primary: 'Inter', sans-serif;
  --font-display: 'Outfit', sans-serif;
  --font-mono: 'Courier New', Courier, monospace;
  
  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  
  --border-radius-sm: 6px;
  --border-radius-md: 12px;
  --border-radius-lg: 16px;
  --border-radius-xl: 24px;
  
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 8px 20px rgba(0, 0, 0, 0.08);
  --shadow-lg: 0 16px 36px rgba(0, 0, 0, 0.12);
  
  --sidebar-width: 280px;
}

/* Dark Theme (Default) */
html[data-theme="dark"] {
  --bg-primary: #0a0b10;
  --bg-secondary: #12131a;
  --bg-card: rgba(22, 24, 35, 0.65);
  --bg-glass: rgba(18, 19, 26, 0.75);
  
  --text-primary: #f3f4f6;
  --text-secondary: #9ca3af;
  --text-muted: #6b7280;
  
  --border-color: rgba(255, 255, 255, 0.08);
  --border-focus: #6366f1;
  
  --accent-color: #6366f1;
  --accent-hover: #4f46e5;
  --accent-light: rgba(99, 102, 241, 0.15);
  
  --success: #10b981;
  --success-light: rgba(16, 185, 129, 0.15);
  --warning: #f59e0b;
  --error: #ef4444;
  --error-light: rgba(239, 68, 68, 0.15);
  
  --selection: rgba(99, 102, 241, 0.3);
  --glow: 0 0 20px rgba(99, 102, 241, 0.25);
  
  --card-hover-bg: rgba(28, 30, 44, 0.8);
  --input-bg: rgba(10, 11, 16, 0.8);
}

/* Light Theme */
html[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-card: rgba(255, 255, 255, 0.8);
  --bg-glass: rgba(255, 255, 255, 0.85);
  
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  
  --border-color: rgba(0, 0, 0, 0.08);
  --border-focus: #4f46e5;
  
  --accent-color: #4f46e5;
  --accent-hover: #3730a3;
  --accent-light: rgba(79, 70, 229, 0.1);
  
  --success: #10b981;
  --success-light: rgba(16, 185, 129, 0.1);
  --warning: #d97706;
  --error: #dc2626;
  --error-light: rgba(220, 38, 38, 0.1);
  
  --selection: rgba(79, 70, 229, 0.2);
  --glow: 0 0 20px rgba(79, 70, 229, 0.15);
  
  --card-hover-bg: rgba(255, 255, 255, 0.95);
  --input-bg: #ffffff;
}

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

body {
  font-family: var(--font-primary);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.5;
  overflow-x: hidden;
  transition: background-color var(--transition-normal), color var(--transition-normal);
  -webkit-font-smoothing: antialiased;
}

::selection {
  background-color: var(--selection);
}

/* Scrollbars */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: var(--border-radius-sm);
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* ==========================================================================
   Layout Grid & Shell
   ========================================================================== */
.app-container {
  display: flex;
  min-height: 100vh;
  position: relative;
}

/* Sidebar Styling */
.sidebar {
  width: var(--sidebar-width);
  background-color: var(--bg-secondary);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  bottom: 0;
  left: 0;
  z-index: 100;
  transition: transform var(--transition-normal), background-color var(--transition-normal);
}

.sidebar-header {
  padding: 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.25rem;
  letter-spacing: -0.5px;
  color: var(--text-primary);
}

.logo-icon {
  color: var(--accent-color);
  stroke-width: 2.5;
  width: 24px;
  height: 24px;
}

.sidebar-toggle-btn {
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  padding: 4px;
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
}

.search-box {
  padding: 0 16px 16px;
  position: relative;
}

.search-icon {
  position: absolute;
  left: 28px;
  top: 50%;
  transform: translateY(-70%);
  color: var(--text-muted);
  width: 16px;
  height: 16px;
  pointer-events: none;
}

.search-box input {
  width: 100%;
  padding: 10px 12px 10px 36px;
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.875rem;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-box input:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--accent-light);
}

.sidebar-nav {
  flex: 1;
  overflow-y: auto;
  padding: 0 16px 24px;
}

.nav-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.nav-category {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-muted);
  letter-spacing: 1px;
  padding: 16px 12px 8px;
}

.nav-item {
  width: 100%;
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  background: none;
  border: none;
  border-radius: var(--border-radius-md);
  color: var(--text-secondary);
  font-family: var(--font-primary);
  font-size: 0.9rem;
  font-weight: 500;
  text-align: left;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.nav-item i {
  width: 18px;
  height: 18px;
  stroke-width: 2;
}

.nav-item:hover {
  background-color: var(--border-color);
  color: var(--text-primary);
}

.nav-item.active {
  background-color: var(--accent-light);
  color: var(--accent-color);
  font-weight: 600;
}

.sidebar-footer {
  padding: 16px;
  border-top: 1px solid var(--border-color);
}

.theme-toggle-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 10px;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.theme-toggle-btn:hover {
  background-color: var(--border-color);
}

html[data-theme="dark"] .sun-icon { display: block; }
html[data-theme="dark"] .moon-icon { display: none; }
html[data-theme="light"] .sun-icon { display: none; }
html[data-theme="light"] .moon-icon { display: block; }

/* Main Content Panel */
.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  padding: 32px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: margin-left var(--transition-normal);
}

.mobile-only {
  display: none !important;
}

/* Viewport structure */
.view-panel {
  flex: 1;
  position: relative;
}

.view-section {
  display: none;
  animation: fadeIn var(--transition-normal) forwards;
}

.view-section.active-section {
  display: block;
}

@keyframes fadeIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ==========================================================================
   Dashboard View Styles
   ========================================================================== */
.hero {
  margin-bottom: 40px;
  max-width: 800px;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: 2.75rem;
  font-weight: 800;
  letter-spacing: -1px;
  margin-bottom: 16px;
  line-height: 1.15;
  background: linear-gradient(135deg, var(--text-primary) 30%, var(--accent-color));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero p {
  font-size: 1.1rem;
  color: var(--text-secondary);
}

/* Dashboard Grid */
.dashboard-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 24px;
}

.tool-card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  padding: 24px;
  display: flex;
  flex-direction: column;
  cursor: pointer;
  transition: all var(--transition-normal);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  position: relative;
  overflow: hidden;
}

.tool-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--accent-color);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.tool-card:hover {
  background-color: var(--card-hover-bg);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md), var(--glow);
  border-color: rgba(99, 102, 241, 0.4);
}

.tool-card:hover::before {
  opacity: 1;
}

.tool-card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--border-radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  color: #fff;
}

/* Card Icon Colors using HSL gradients */
.qr-icon { background: linear-gradient(135deg, #ec4899, #f43f5e); }
.json-icon { background: linear-gradient(135deg, #3b82f6, #06b6d4); }
.password-icon { background: linear-gradient(135deg, #10b981, #059669); }
.b64-icon { background: linear-gradient(135deg, #8b5cf6, #d946ef); }
.text-icon { background: linear-gradient(135deg, #f59e0b, #eab308); }
.color-icon { background: linear-gradient(135deg, #f43f5e, #e11d48); }
.math-icon { background: linear-gradient(135deg, #6366f1, #3b82f6); }

.tool-card-icon i {
  width: 24px;
  height: 24px;
  stroke-width: 2;
}

.tool-card h3 {
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.tool-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
  line-height: 1.5;
  margin-bottom: 20px;
  flex: 1;
}

.tool-card-action {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent-color);
  display: flex;
  align-items: center;
  gap: 8px;
  transition: gap var(--transition-fast);
}

.tool-card-action i {
  width: 16px;
  height: 16px;
}

.tool-card:hover .tool-card-action {
  gap: 12px;
}

/* ==========================================================================
   Tool Views Shared Layout
   ========================================================================== */
.section-header {
  display: flex;
  align-items: center;
  gap: 20px;
  margin-bottom: 32px;
}

.section-header h2 {
  font-family: var(--font-display);
  font-size: 2rem;
  font-weight: 800;
  letter-spacing: -0.5px;
}

.back-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  color: var(--text-secondary);
  font-family: var(--font-primary);
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

.back-btn i {
  width: 16px;
  height: 16px;
}

/* Tool Columns Layout */
.tool-layout {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 32px;
  align-items: start;
}

.tool-input-panel, .tool-output-panel {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  padding: 32px;
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
}

.wide-panel {
  grid-column: span 2;
}

/* Form Styling */
.form-group {
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 20px;
}

.form-group label {
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--text-secondary);
}

.form-row {
  display: flex;
  gap: 20px;
  margin-bottom: 20px;
}

.form-row .form-group {
  flex: 1;
  margin-bottom: 0;
}

/* Inputs & Form Controls */
input[type="text"],
input[type="number"],
textarea,
select {
  width: 100%;
  padding: 12px 16px;
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  color: var(--text-primary);
  font-family: var(--font-primary);
  font-size: 0.95rem;
  transition: all var(--transition-fast);
}

input[type="text"]:focus,
input[type="number"]:focus,
textarea:focus,
select:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--accent-light);
}

textarea {
  resize: vertical;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: var(--border-radius-md);
  font-family: var(--font-primary);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  border: none;
}

.btn-primary {
  background-color: var(--accent-color);
  color: #ffffff;
}

.btn-primary:hover {
  background-color: var(--accent-hover);
  box-shadow: var(--shadow-md), 0 0 12px rgba(99, 102, 241, 0.4);
}

.btn-secondary {
  background-color: var(--border-color);
  color: var(--text-primary);
}

.btn-secondary:hover {
  background-color: rgba(255, 255, 255, 0.15);
}

html[data-theme="light"] .btn-secondary:hover {
  background-color: rgba(0, 0, 0, 0.05);
}

.btn-outline {
  background: transparent;
  border: 1px solid var(--border-color);
  color: var(--text-primary);
}

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

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.w-full {
  width: 100%;
}

.margin-top-md {
  margin-top: 20px;
}

/* ==========================================================================
   Tool 1: QR Code Custom Styles
   ========================================================================== */
.color-picker-wrapper {
  display: flex;
  gap: 12px;
}

.color-picker-wrapper input[type="color"] {
  -webkit-appearance: none;
  border: none;
  width: 48px;
  height: 48px;
  border-radius: var(--border-radius-md);
  cursor: pointer;
  background: none;
}

.color-picker-wrapper input[type="color"]::-webkit-color-swatch-wrapper {
  padding: 0;
}

.color-picker-wrapper input[type="color"]::-webkit-color-swatch {
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
}

.qr-preview-box {
  background-color: #ffffff;
  border-radius: var(--border-radius-lg);
  padding: 24px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 280px;
  margin-bottom: 24px;
  border: 1px solid var(--border-color);
}

html[data-theme="dark"] .qr-preview-box {
  background-color: #12131a;
}

#qrcode-canvas-container {
  display: flex;
  justify-content: center;
}

#qrcode-canvas-container canvas {
  max-width: 100%;
  height: auto !important;
  border-radius: var(--border-radius-md);
}

.preview-placeholder {
  color: var(--text-muted);
  font-size: 0.9rem;
  text-align: center;
}

.action-buttons-group {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

/* ==========================================================================
   Tool 2: JSON Formatter Styles
   ========================================================================== */
.json-workspace {
  display: grid;
  grid-template-columns: 1fr 120px 1fr;
  gap: 20px;
  align-items: stretch;
  min-height: 500px;
  margin-bottom: 20px;
}

.editor-container {
  display: flex;
  flex-direction: column;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  overflow: hidden;
}

.editor-header {
  padding: 12px 20px;
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.editor-title {
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-secondary);
  letter-spacing: 0.5px;
}

.editor-actions {
  display: flex;
  gap: 8px;
}

.editor-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 6px;
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  transition: all var(--transition-fast);
}

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

.editor-btn i {
  width: 16px;
  height: 16px;
}

.json-workspace textarea {
  flex: 1;
  border: none;
  border-radius: 0;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  padding: 20px;
  background-color: transparent;
  resize: none;
  min-height: 400px;
}

.json-workspace textarea:focus {
  box-shadow: none;
}

.read-only-editor {
  background-color: rgba(0, 0, 0, 0.05) !important;
}

html[data-theme="dark"] .read-only-editor {
  background-color: rgba(0, 0, 0, 0.15) !important;
}

.json-actions-divider {
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 12px;
  padding: 0 10px;
}

.json-status-alert {
  padding: 16px 20px;
  border-radius: var(--border-radius-md);
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.9rem;
  font-weight: 500;
  transition: all var(--transition-fast);
  border: 1px solid var(--border-color);
}

.json-status-alert.hide {
  display: none;
}

.json-status-alert.status-success {
  background-color: var(--success-light);
  color: var(--success);
  border-color: rgba(16, 185, 129, 0.3);
}

.json-status-alert.status-error {
  background-color: var(--error-light);
  color: var(--error);
  border-color: rgba(239, 68, 68, 0.3);
}

.status-icon {
  width: 18px;
  height: 18px;
}

/* ==========================================================================
   Tool 3: Password Generator Styles
   ========================================================================== */
.range-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 4px;
}

.badge {
  background-color: var(--accent-light);
  color: var(--accent-color);
  padding: 4px 8px;
  border-radius: var(--border-radius-sm);
  font-weight: 700;
  font-size: 0.85rem;
}

.range-slider {
  -webkit-appearance: none;
  width: 100%;
  height: 6px;
  border-radius: var(--border-radius-sm);
  background: var(--border-color);
  outline: none;
}

.range-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--accent-color);
  cursor: pointer;
  transition: transform var(--transition-fast);
}

.range-slider::-webkit-slider-thumb:hover {
  transform: scale(1.2);
}

.checkbox-group-container {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 24px;
}

/* Custom Styled Checkbox */
.custom-checkbox {
  display: flex;
  align-items: center;
  position: relative;
  padding-left: 32px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  user-select: none;
}

.custom-checkbox input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
  height: 0;
  width: 0;
}

.checkmark {
  position: absolute;
  top: 50%;
  left: 0;
  transform: translateY(-50%);
  height: 20px;
  width: 20px;
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-sm);
  transition: all var(--transition-fast);
}

.custom-checkbox:hover input ~ .checkmark {
  border-color: var(--text-muted);
}

.custom-checkbox input:checked ~ .checkmark {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
}

.checkmark:after {
  content: "";
  position: absolute;
  display: none;
}

.custom-checkbox input:checked ~ .checkmark:after {
  display: block;
}

.custom-checkbox .checkmark:after {
  left: 7px;
  top: 3px;
  width: 5px;
  height: 10px;
  border: solid white;
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}

/* Password Display Box */
.password-display-wrapper {
  display: flex;
  position: relative;
  margin-bottom: 24px;
}

.password-display-wrapper input {
  width: 100%;
  padding: 16px 56px 16px 20px;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 600;
  text-align: center;
}

.btn-copy-inline {
  position: absolute;
  right: 8px;
  top: 50%;
  transform: translateY(-50%);
  background: transparent;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 10px;
  border-radius: var(--border-radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.btn-copy-inline:hover {
  background-color: var(--border-color);
  color: var(--text-primary);
}

.btn-copy-inline i {
  width: 20px;
  height: 20px;
}

/* Strength Meter */
.password-strength-box {
  margin-bottom: 24px;
}

.strength-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  display: block;
  margin-bottom: 8px;
}

.strength-meter {
  height: 6px;
  background-color: var(--border-color);
  border-radius: var(--border-radius-sm);
  overflow: hidden;
  margin-bottom: 6px;
}

.strength-bar {
  height: 100%;
  border-radius: var(--border-radius-sm);
  transition: width var(--transition-normal), background-color var(--transition-fast);
}

.strength-text {
  font-size: 0.85rem;
  font-weight: 700;
}

.strength-bar.weak { background-color: var(--error); }
.strength-bar.medium { background-color: var(--warning); }
.strength-bar.strong { background-color: var(--success); }

.strength-text.weak { color: var(--error); }
.strength-text.medium { color: var(--warning); }
.strength-text.strong { color: var(--success); }

.password-tips {
  border-top: 1px solid var(--border-color);
  padding-top: 20px;
}

.password-tips h4 {
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--success);
  margin-bottom: 8px;
}

.password-tips h4 i {
  width: 18px;
  height: 18px;
}

.password-tips p {
  font-size: 0.85rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ==========================================================================
   Tool 4: Base64 Styles
   ========================================================================== */
.tab-container {
  display: flex;
  border-bottom: 1px solid var(--border-color);
  gap: 20px;
}

.tab-btn {
  background: none;
  border: none;
  padding: 12px 4px;
  font-family: var(--font-primary);
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  position: relative;
  transition: color var(--transition-fast);
}

.tab-btn:hover {
  color: var(--text-primary);
}

.tab-btn.active {
  color: var(--accent-color);
}

.tab-btn.active::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: 0;
  right: 0;
  height: 2px;
  background-color: var(--accent-color);
}

.label-with-action {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.text-btn-action {
  background: none;
  border: none;
  color: var(--accent-color);
  font-family: var(--font-primary);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 6px;
  transition: opacity var(--transition-fast);
}

.text-btn-action:hover {
  opacity: 0.8;
}

.text-btn-action i {
  width: 14px;
  height: 14px;
}

/* ==========================================================================
   Tool 5: Text Converter Styles
   ========================================================================== */
.text-actions-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 12px;
}

.txt-action-btn {
  padding: 10px;
  font-size: 0.85rem;
}

.text-stats-panel h3 {
  font-family: var(--font-display);
  font-size: 1.25rem;
  margin-bottom: 20px;
}

.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.stat-box {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 16px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.stat-num {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--accent-color);
  margin-bottom: 4px;
}

.stat-lbl {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  color: var(--text-secondary);
  letter-spacing: 0.5px;
  text-align: center;
}

/* ==========================================================================
   Tool 6: Color Palette Styles
   ========================================================================== */
.palette-workspace {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-lg);
  padding: 32px;
}

.palette-toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 20px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}

.palette-toolbar .form-group {
  margin-bottom: 0;
}

.flex-row {
  flex-direction: row;
}

.align-center {
  align-items: center;
}

.gap-sm {
  gap: 10px;
}

.palette-actions {
  display: flex;
  gap: 12px;
}

.palette-colors-display {
  display: flex;
  height: 320px;
  border-radius: var(--border-radius-lg);
  overflow: hidden;
  border: 1px solid var(--border-color);
}

.color-column {
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
  align-items: center;
  padding: 24px 12px;
  position: relative;
  transition: flex var(--transition-normal), background-color var(--transition-fast);
  cursor: pointer;
}

.color-column:hover {
  flex: 1.25;
}

.color-column-actions {
  position: absolute;
  top: 20px;
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.color-column:hover .color-column-actions {
  opacity: 1;
}

.color-copy-btn {
  background: rgba(0, 0, 0, 0.4);
  border: 1px solid rgba(255, 255, 255, 0.2);
  color: #ffffff;
  padding: 8px;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(4px);
}

.color-copy-btn:hover {
  background: rgba(0, 0, 0, 0.6);
}

.color-copy-btn i {
  width: 16px;
  height: 16px;
}

.color-column-details {
  display: flex;
  flex-direction: column;
  align-items: center;
  background: rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(4px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  padding: 12px;
  border-radius: var(--border-radius-md);
  width: 100%;
  max-width: 120px;
  text-align: center;
  color: #ffffff;
  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
}

.color-hex {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: 0.95rem;
  margin-bottom: 4px;
}

.color-rgb {
  font-size: 0.7rem;
  opacity: 0.85;
}

/* ==========================================================================
   Tool 7: Rule of Three Calculator Styles
   ========================================================================== */
.proportion-type-selector {
  display: flex;
  gap: 24px;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 16px;
}

/* Custom Radio Styling */
.custom-radio {
  display: flex;
  align-items: center;
  position: relative;
  padding-left: 28px;
  cursor: pointer;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  user-select: none;
}

.custom-radio input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
}

.radiomark {
  position: absolute;
  top: 50%;
  left: 0;
  transform: translateY(-50%);
  height: 18px;
  width: 18px;
  background-color: var(--input-bg);
  border: 1px solid var(--border-color);
  border-radius: 50%;
  transition: all var(--transition-fast);
}

.custom-radio:hover input ~ .radiomark {
  border-color: var(--text-muted);
}

.custom-radio input:checked ~ .radiomark {
  background-color: var(--accent-color);
  border-color: var(--accent-color);
}

.radiomark:after {
  content: "";
  position: absolute;
  display: none;
}

.custom-radio input:checked ~ .radiomark:after {
  display: block;
}

.custom-radio .radiomark:after {
  top: 5px;
  left: 5px;
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: white;
}

/* Math Grid */
.math-grid-container {
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.math-row {
  display: flex;
  align-items: flex-end;
  gap: 16px;
}

.math-col {
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.math-col label {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-muted);
}

.math-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  height: 48px;
  color: var(--text-muted);
}

.math-arrow i {
  width: 20px;
  height: 20px;
}

.highlight-col input {
  background-color: var(--accent-light);
  border-color: var(--accent-color);
  color: var(--accent-color);
  font-weight: 700;
}

.math-result-input {
  font-size: 1.1rem !important;
}

.rot-explanation-panel h3 {
  font-family: var(--font-display);
  font-size: 1.15rem;
  margin-bottom: 16px;
}

.formula-box {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 20px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  margin-bottom: 20px;
}

#formula-text {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-primary);
}

.formula-result {
  font-family: var(--font-mono);
  font-size: 1.1rem;
  color: var(--accent-color);
  font-weight: 600;
}

.rot-explanation-panel p {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ==========================================================================
   Toast Notification Styling
   ========================================================================== */
.toast-container {
  position: fixed;
  top: 24px;
  right: 24px;
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: 12px;
  pointer-events: none;
}

.toast {
  background-color: var(--bg-glass);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  padding: 14px 20px;
  box-shadow: var(--shadow-lg);
  color: var(--text-primary);
  font-size: 0.9rem;
  font-weight: 600;
  display: flex;
  align-items: center;
  gap: 12px;
  min-width: 280px;
  pointer-events: auto;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  transform: translateX(120%);
  animation: slideIn var(--transition-normal) forwards;
}

.toast.toast-success {
  border-left: 4px solid var(--success);
}

.toast.toast-success i {
  color: var(--success);
}

.toast.toast-error {
  border-left: 4px solid var(--error);
}

.toast.toast-error i {
  color: var(--error);
}

.toast.toast-info {
  border-left: 4px solid var(--accent-color);
}

.toast.toast-info i {
  color: var(--accent-color);
}

.toast i {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}

.toast-message {
  flex: 1;
}

.toast.toast-fadeout {
  animation: slideOut var(--transition-normal) forwards;
}

@keyframes slideIn {
  to {
    transform: translateX(0);
  }
}

@keyframes slideOut {
  from {
    transform: translateX(0);
    opacity: 1;
  }
  to {
    transform: translateX(120%);
    opacity: 0;
  }
}

/* ==========================================================================
   Responsive Media Queries
   ========================================================================== */

/* Laptop / Medium Desktops */
@screen-lg {
  /* custom breakpoints handled below */
}

@media (max-width: 1024px) {
  .json-workspace {
    grid-template-columns: 1fr;
    grid-template-rows: auto auto auto;
    min-height: auto;
  }
  
  .json-actions-divider {
    flex-direction: row;
    padding: 10px 0;
  }
}

/* Tablet & Mobile Screens */
@media (max-width: 768px) {
  :root {
    --sidebar-width: 100%;
  }
  
  .app-container {
    flex-direction: column;
  }
  
  /* Sidebar responsive logic */
  .sidebar {
    transform: translateX(-100%);
    width: 280px;
    box-shadow: var(--shadow-lg);
  }
  
  .sidebar.open {
    transform: translateX(0);
  }
  
  /* Main Content responsive logic */
  .main-content {
    margin-left: 0;
    padding: 20px;
    padding-top: 80px; /* space for mobile header */
  }
  
  .mobile-only {
    display: flex !important;
  }
  
  /* Mobile Header Navigation */
  .mobile-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: 64px;
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 20px;
    z-index: 90;
  }
  
  .mobile-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-family: var(--font-display);
    font-weight: 800;
    font-size: 1.15rem;
    color: var(--text-primary);
  }
  
  .mobile-logo i {
    color: var(--accent-color);
    width: 20px;
    height: 20px;
  }
  
  .menu-btn {
    background: none;
    border: none;
    color: var(--text-primary);
    cursor: pointer;
    padding: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
  }
  
  .menu-btn i {
    width: 24px;
    height: 24px;
  }
  
  /* Hero section on mobile */
  .hero h1 {
    font-size: 2rem;
  }
  
  /* Tool layout on mobile */
  .tool-layout {
    grid-template-columns: 1fr;
    gap: 20px;
  }
  
  .wide-panel {
    grid-column: span 1;
  }
  
  .palette-colors-display {
    flex-direction: column;
    height: 480px;
  }
  
  .color-column {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    padding: 16px 20px;
  }
  
  .color-column:hover {
    flex: 1.25;
  }
  
  .color-column-actions {
    position: relative;
    top: auto;
    opacity: 1;
  }
  
  .color-column-details {
    flex-direction: row;
    justify-content: space-between;
    align-items: center;
    max-width: none;
    width: auto;
    gap: 16px;
    padding: 8px 12px;
  }
  
  .color-hex {
    margin-bottom: 0;
  }
  
  .stats-grid {
    grid-template-columns: 1fr;
  }
  
  .math-row {
    flex-direction: column;
    align-items: stretch;
    gap: 10px;
  }
  
  .math-arrow {
    height: 24px;
    transform: rotate(90deg);
  }
}

/* ==========================================================================
   Authentication Overlay Styles (Gated Portal)
   ========================================================================== */
.auth-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: var(--bg-primary);
  background-image: radial-gradient(circle at 10% 20%, rgba(99, 102, 241, 0.1) 0%, transparent 40%),
                    radial-gradient(circle at 90% 80%, rgba(99, 102, 241, 0.08) 0%, transparent 40%);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10000; /* overlay above everything */
  transition: opacity var(--transition-normal), visibility var(--transition-normal);
  padding: 20px;
}

.auth-overlay.hide {
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}

.auth-card {
  width: 100%;
  max-width: 420px;
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-xl);
  padding: 40px;
  box-shadow: var(--shadow-lg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  animation: authScaleIn var(--transition-normal) forwards;
}

@keyframes authScaleIn {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

.auth-header {
  text-align: center;
  margin-bottom: 32px;
}

.auth-logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 1.5rem;
  color: var(--text-primary);
  margin-bottom: 16px;
}

.auth-logo-icon {
  color: var(--accent-color);
  width: 28px;
  height: 28px;
  stroke-width: 2.5;
}

.auth-header h2 {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 800;
  margin-bottom: 8px;
  color: var(--text-primary);
}

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

.auth-credentials-hint {
  margin-top: 24px;
  padding: 16px;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--border-radius-md);
  font-size: 0.8rem;
}

.hint-title {
  display: flex;
  align-items: center;
  gap: 6px;
  font-weight: 700;
  color: var(--accent-color);
  margin-bottom: 8px;
}

.hint-title i {
  width: 14px;
  height: 14px;
}

.auth-credentials-hint code {
  font-family: var(--font-mono);
  background: var(--input-bg);
  padding: 2px 6px;
  border-radius: 4px;
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

/* User Profile Card in Sidebar */
.user-profile-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px;
  background-color: rgba(255, 255, 255, 0.03);
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
  margin-top: auto;
  transition: all var(--transition-fast);
}

html[data-theme="light"] .user-profile-card {
  background-color: rgba(0, 0, 0, 0.02);
}

.user-profile-card.hide {
  display: none !important;
}

.user-avatar {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent-color), #8b5cf6);
  color: #ffffff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-display);
  font-weight: 700;
  font-size: 0.9rem;
  flex-shrink: 0;
  border: 2px solid var(--border-color);
}

.user-details {
  flex: 1;
  display: flex;
  flex-direction: column;
  min-width: 0; /* allows text truncation */
}

.user-name {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-primary);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.user-email {
  font-size: 0.75rem;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.logout-btn {
  background: none;
  border: none;
  color: var(--text-secondary);
  cursor: pointer;
  padding: 8px;
  border-radius: var(--border-radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.logout-btn:hover {
  background-color: var(--error-light);
  color: var(--error);
}

.logout-btn i {
  width: 18px;
  height: 18px;
}