/* ==================== style.css - Refactored & Optimized ==================== */
/* Table of Contents:
   1. CSS Variables & Theme
   2. Reset & Base Styles
   3. Layout Components (Navbar, App Layout, Sidebar, Main Content)
   4. Core UI Components (Cards, Buttons, Inputs, Keypad, Modal)
   5. Feature-Specific Styles (CGPA, Statistics, Matrix, Advanced Grid)
   6. Animations
   7. Utility Classes
   8. Responsive Design (Single Mobile Media Query)
*/

/* ===== 1. CSS VARIABLES & THEME ===== */
:root {
  /* Spacing System */
  --space-unit: 8px;
  --space-xs: calc(var(--space-unit) * 0.5);
  --space-sm: var(--space-unit);
  --space-md: calc(var(--space-unit) * 2);
  --space-lg: calc(var(--space-unit) * 3);
  --space-xl: calc(var(--space-unit) * 4);
  
  /* Border Radius */
  --radius-sm: calc(var(--space-unit) * 1);
  --radius-md: calc(var(--space-unit) * 2);
  --radius-lg: calc(var(--space-unit) * 3);
  
  /* Transitions */
  --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-drawer: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
  
  /* Light Theme (Default) */
  --bg-gradient: linear-gradient(145deg, #f6f9fc 0%, #e9f0f5 100%);
  --surface: rgba(255, 255, 255, 0.7);
  --surface-solid: #ffffff;
  --text-primary: #1a2639;
  --text-secondary: #2c3e50;
  --primary: #4361ee;
  --primary-dark: #3a56d4;
  --accent: #f72585;
  --neutral-100: #f8fafd;
  --neutral-200: #e9eef3;
  --neutral-300: #cbd5e1;
  --glass-border: rgba(255, 255, 255, 0.5);
  --shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.1);
  --key-hint: #64748b;
  --sidebar-width: 260px;
  --navbar-height: 70px;
}

/* Dark Theme */
.dark {
  --bg-gradient: linear-gradient(145deg, #121826 0%, #1a1f30 100%);
  --surface: rgba(30, 35, 55, 0.8);
  --surface-solid: #222a41;
  --text-primary: #edf2f7;
  --text-secondary: #cbd5e1;
  --primary: #4895ef;
  --primary-dark: #3a7bc8;
  --accent: #f472b6;
  --neutral-100: #2d3748;
  --neutral-200: #364153;
  --neutral-300: #4a5568;
  --glass-border: rgba(255, 255, 255, 0.1);
  --shadow: 0 10px 30px -5px rgba(0, 0, 0, 0.5);
  --key-hint: #94a3b8;
}

/* ===== 2. RESET & BASE STYLES ===== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background: var(--bg-gradient);
  color: var(--text-primary);
  min-height: 100vh;
  line-height: 1.5;
  transition: background 0.3s, color 0.3s;
}

/* Glassmorphism Base */
.glass {
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(180%);
  -webkit-backdrop-filter: blur(16px) saturate(180%);
  border: 1px solid var(--glass-border);
  box-shadow: var(--shadow);
}

/* ===== 3. LAYOUT COMPONENTS ===== */
/* Navbar */
.navbar {
  position: sticky;
  top: 0;
  z-index: 100;
  padding: var(--space-sm) var(--space-md);
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(180%);
  border-bottom: 1px solid var(--glass-border);
  height: var(--navbar-height);
}

.nav-container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  max-width: 1400px;
  margin: 0 auto;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-size: 1.25rem;
}

.logo i {
  color: var(--primary);
  font-size: 2rem;
}

.logo h1 {
  font-size: 1.25rem;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.nav-controls {
  display: flex;
  gap: var(--space-xs);
}

.icon-btn {
  background: transparent;
  border: none;
  font-size: 1.4rem;
  color: var(--text-primary);
  cursor: pointer;
  padding: var(--space-xs);
  border-radius: 50%;
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
  min-width: 44px;
  min-height: 44px;
}

.icon-btn:hover {
  background: var(--neutral-300);
  transform: scale(1.1);
}

.icon-btn:active {
  transform: scale(0.95);
}

.mobile-menu {
  display: none;
}

/* App Layout */
.app-layout {
  display: flex;
  max-width: 1400px;
  margin: var(--space-lg) auto;
  gap: var(--space-lg);
  padding: 0 var(--space-md);
  min-height: calc(100vh - var(--navbar-height) - var(--space-lg) * 2);
}

/* Sidebar - Desktop Version (min-width: 769px) */
.sidebar {
  width: var(--sidebar-width);
  border-radius: var(--radius-lg);
  padding: var(--space-lg) 0;
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(180%);
  border: 1px solid var(--glass-border);
  box-shadow: var(--shadow);
  height: fit-content;
  position: sticky;
  top: calc(var(--navbar-height) + var(--space-lg));
  align-self: flex-start;
  overflow-y: auto;
  max-height: calc(100vh - var(--navbar-height) - var(--space-lg) * 2);
  transition: var(--transition-drawer);
  
  /* Scrollbar styling */
  scrollbar-width: thin;
  scrollbar-color: var(--primary) var(--neutral-300);
}

.sidebar::-webkit-scrollbar {
  width: 6px;
}

.sidebar::-webkit-scrollbar-track {
  background: var(--neutral-300);
  border-radius: 10px;
}

.sidebar::-webkit-scrollbar-thumb {
  background: var(--primary);
  border-radius: 10px;
}

.sidebar::-webkit-scrollbar-thumb:hover {
  background: var(--primary-dark);
}

.sidebar nav ul {
  list-style: none;
}

.nav-section {
  padding: var(--space-md) var(--space-lg) var(--space-xs);
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--key-hint);
  font-weight: 600;
}

.nav-link {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-sm) var(--space-lg);
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
  border-left: 4px solid transparent;
}

.nav-link i {
  width: 24px;
  font-size: 1.2rem;
  text-align: center;
}

.nav-link:hover,
.nav-link.active {
  background: var(--neutral-100);
  color: var(--primary);
  border-left-color: var(--primary);
}

/* Main Content */
.main-content {
  flex: 1;
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(180%);
  border: 1px solid var(--glass-border);
  box-shadow: var(--shadow);
  transition: var(--transition);
  min-width: 0; /* Prevents flex overflow */
}

/* ===== 4. CORE UI COMPONENTS ===== */
/* Cards */
.calc-card {
  display: none;
}

.calc-card.active-calc {
  display: block;
  animation: fadeSlide 0.4s ease-out;
}

/* Headings */
h2 {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
  font-weight: 500;
  letter-spacing: -0.02em;
  flex-wrap: wrap;
  font-size: 1.5rem;
}

.badge {
  background: var(--primary);
  color: white;
  padding: var(--space-xs) var(--space-sm);
  border-radius: 30px;
  font-size: 0.8rem;
  margin-left: auto;
  cursor: pointer;
}

.shortcut-hint {
  font-size: 0.8rem;
  color: var(--key-hint);
  font-weight: normal;
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

/* Display Input */
.calc-display {
  width: 100%;
  margin-bottom: var(--space-lg);
}

.calc-display input {
  width: 100%;
  padding: var(--space-lg) var(--space-xl);
  font-size: 2rem;
  background: var(--neutral-100);
  border: 2px solid transparent;
  border-radius: var(--radius-md);
  text-align: right;
  color: var(--text-primary);
  outline: none;
  transition: var(--transition);
}

.calc-display input:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.3);
}

/* Buttons */
.action-btn {
  background: var(--primary);
  color: white;
  border: none;
  padding: var(--space-sm) var(--space-lg);
  border-radius: 40px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  min-height: 44px;
}

.action-btn:hover {
  background: var(--primary-dark);
  transform: translateY(-2px);
}

.action-btn.small {
  padding: var(--space-xs) var(--space-sm);
  font-size: 0.9rem;
}

.reset-btn {
  background: var(--neutral-300);
  color: var(--text-primary);
  border: none;
  padding: var(--space-sm) var(--space-lg);
  border-radius: 40px;
  cursor: pointer;
  transition: var(--transition);
  min-height: 44px;
}

.reset-btn:hover {
  background: var(--neutral-200);
  transform: translateY(-2px);
}

.reset-btn.small {
  padding: var(--space-xs) var(--space-sm);
  font-size: 0.9rem;
}

/* Keypad */
.keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--space-sm);
  margin-bottom: var(--space-md);
}

.sci-keypad {
  grid-template-columns: repeat(5, 1fr);
}

.btn {
  padding: var(--space-md) var(--space-xs);
  font-size: 1.2rem;
  font-weight: 600;
  border: none;
  background: var(--neutral-100);
  color: var(--text-primary);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  box-shadow: 0 4px 6px rgba(0, 0, 0, 0.03);
  position: relative;
  overflow: hidden;
  min-height: 52px;
}

.btn:hover {
  transform: scale(0.98);
  background: var(--neutral-300);
}

.btn:active {
  transform: scale(0.96);
}

.btn.key-press {
  transform: scale(0.95);
  background: var(--primary);
  color: white;
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.5);
}

.btn::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0;
  height: 0;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.5);
  transform: translate(-50%, -50%);
  transition: width 0.3s, height 0.3s;
}

.btn:active::after {
  width: 200px;
  height: 200px;
}

.op, .fn {
  background: var(--primary);
  color: white;
}

.eq {
  background: var(--accent);
  color: white;
}

.reset {
  background: var(--neutral-300);
}

.keyboard-hint {
  margin-top: var(--space-md);
  padding: var(--space-xs) var(--space-md);
  background: var(--neutral-100);
  border-radius: 30px;
  font-size: 0.9rem;
  color: var(--key-hint);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

/* Input Groups */
.input-group {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-md);
  margin-bottom: var(--space-lg);
}

.input-group input {
  flex: 1 1 200px;
  padding: var(--space-sm) var(--space-md);
  border-radius: var(--radius-md);
  border: 1px solid var(--neutral-300);
  background: var(--surface-solid);
  color: var(--text-primary);
  font-size: 1rem;
}

.input-group input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
}

/* Modal */
.modal {
  display: none;
  position: fixed;
  z-index: 1000;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(5px);
  align-items: center;
  justify-content: center;
}

.modal.show {
  display: flex;
}

.modal-content {
  max-width: 800px;
  width: 90%;
  max-height: 80vh;
  overflow-y: auto;
  padding: var(--space-xl);
  border-radius: var(--radius-lg);
  position: relative;
  background: var(--surface);
  backdrop-filter: blur(16px) saturate(180%);
  border: 1px solid var(--glass-border);
}

.close-modal {
  position: absolute;
  right: var(--space-lg);
  top: var(--space-sm);
  font-size: 2rem;
  cursor: pointer;
  color: var(--text-secondary);
  background: none;
  border: none;
  width: 44px;
  height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
}

.close-modal:hover {
  background: var(--neutral-300);
}

.shortcut-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-lg);
}

.shortcut-category h3 {
  margin-bottom: var(--space-sm);
  color: var(--primary);
}

.shortcut-category ul {
  list-style: none;
}

.shortcut-category li {
  margin-bottom: var(--space-xs);
}

kbd {
  background: var(--neutral-300);
  color: var(--text-primary);
  padding: 3px 6px;
  border-radius: 4px;
  font-family: monospace;
  font-size: 0.9rem;
}

/* ===== 5. FEATURE-SPECIFIC STYLES ===== */
/* Advanced Grid (used across features) */
.advanced-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
  margin-top: var(--space-md);
}

.sub-calc {
  background: var(--neutral-100);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  border: 1px solid var(--neutral-300);
}

.sub-calc h3 {
  font-size: 1.1rem;
  margin-bottom: var(--space-md);
  color: var(--primary);
}

.sub-calc input,
.sub-calc select {
  width: 100%;
  padding: var(--space-sm);
  margin: var(--space-xs) 0;
  border-radius: var(--radius-md);
  border: 1px solid var(--neutral-300);
  background: var(--surface-solid);
  color: var(--text-primary);
  font-size: 1rem;
}

.sub-calc input:focus,
.sub-calc select:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
}

/* CGPA Calculator */
.semester-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-xs);
  margin-bottom: var(--space-lg);
}

.sem-tab {
  padding: var(--space-xs) var(--space-md);
  background: var(--neutral-100);
  border-radius: 30px;
  cursor: pointer;
  border: 1px solid var(--neutral-300);
  transition: var(--transition);
}

.sem-tab.active {
  background: var(--primary);
  color: white;
  border-color: var(--primary);
}

.semester-card {
  background: var(--neutral-100);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-bottom: var(--space-lg);
  border: 1px solid var(--neutral-300);
}

.semester-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-md);
  flex-wrap: wrap;
  gap: var(--space-sm);
}

.semester-title {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.semester-number-input {
  width: 70px;
  padding: var(--space-xs);
  border: 2px solid var(--primary);
  border-radius: var(--radius-sm);
  background: var(--surface-solid);
  color: var(--text-primary);
  font-weight: 600;
  text-align: center;
}

.semester-controls {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.semester-sgpa {
  background: var(--primary);
  color: white;
  padding: var(--space-xs) var(--space-sm);
  border-radius: 20px;
  font-size: 0.9rem;
  font-weight: 600;
}

.subject-row {
  display: flex;
  gap: var(--space-sm);
  margin-bottom: var(--space-xs);
  align-items: center;
  flex-wrap: wrap;
}

.subject-row input,
.subject-row select {
  padding: var(--space-xs) var(--space-sm);
  border-radius: var(--radius-md);
  border: 1px solid var(--neutral-300);
  background: var(--surface-solid);
  color: var(--text-primary);
}

.subject-row .subject {
  flex: 2;
  min-width: 120px;
}

.subject-row .credit {
  width: 80px;
}

.subject-row .grade {
  width: 100px;
}

.remove-subj {
  background: none;
  border: none;
  color: #ef4444;
  font-size: 1.2rem;
  cursor: pointer;
  padding: var(--space-xs);
  min-width: 44px;
  min-height: 44px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
}

.remove-subj:hover {
  background: rgba(239, 68, 68, 0.1);
}

.cgpa-metrics {
  display: flex;
  gap: var(--space-xl);
  margin: var(--space-lg) 0;
  font-size: 1.2rem;
  flex-wrap: wrap;
  background: linear-gradient(145deg, var(--primary), var(--primary-dark));
  color: white;
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
}

.metric {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
}

.metric span:first-child {
  font-weight: 300;
}

.metric .animated-number {
  font-weight: 700;
  font-size: 2rem;
  color: white;
}

.chart-container {
  height: 200px;
  margin: var(--space-lg) 0;
}

.cgpa-actions {
  display: flex;
  gap: var(--space-md);
  margin: var(--space-lg) 0;
  flex-wrap: wrap;
}

.formula {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-top: var(--space-md);
  font-style: italic;
}

/* Statistics Calculator */
.statistics-container {
  display: flex;
  flex-direction: column;
  gap: var(--space-xl);
}

.number-input-section {
  background: var(--neutral-100);
  padding: var(--space-lg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--neutral-300);
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-lg);
  flex-wrap: wrap;
  gap: var(--space-md);
}

.section-header h3 {
  color: var(--primary);
  margin: 0;
  font-size: 1.2rem;
}

.input-controls {
  display: flex;
  gap: var(--space-xs);
}

.number-fields-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
  max-height: 300px;
  overflow-y: auto;
  padding: var(--space-sm);
  background: var(--surface-solid);
  border-radius: var(--radius-md);
}

.number-field-item {
  position: relative;
}

.number-field-item input {
  width: 100%;
  padding: var(--space-sm);
  border: 2px solid var(--neutral-300);
  border-radius: var(--radius-md);
  background: var(--surface-solid);
  color: var(--text-primary);
  font-size: 1rem;
  text-align: center;
  transition: var(--transition);
}

.number-field-item input:focus {
  border-color: var(--primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
}

.number-field-item .remove-field {
  position: absolute;
  top: -8px;
  right: -8px;
  width: 22px;
  height: 22px;
  border-radius: 50%;
  background: #ef4444;
  color: white;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  opacity: 0;
  transition: var(--transition);
}

.number-field-item:hover .remove-field {
  opacity: 1;
}

.number-field-item .remove-field:hover {
  background: #dc2626;
  transform: scale(1.1);
}

.input-summary {
  display: flex;
  gap: var(--space-lg);
  padding: var(--space-md);
  background: var(--surface-solid);
  border-radius: var(--radius-md);
  border: 1px solid var(--primary);
  flex-wrap: wrap;
}

.input-summary span {
  font-size: 1rem;
}

.input-summary strong {
  color: var(--primary);
  font-size: 1.2rem;
  margin-left: var(--space-xs);
}

.statistics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--space-lg);
  margin: var(--space-lg) 0;
}

.stat-card {
  background: var(--surface-solid);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  text-align: center;
  border: 1px solid var(--neutral-300);
  transition: var(--transition);
}

.stat-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow);
  border-color: var(--primary);
}

.stat-icon {
  font-size: 2.5rem;
  margin-bottom: var(--space-sm);
}

.stat-card h3 {
  color: var(--text-primary);
  margin-bottom: var(--space-md);
  font-size: 1.2rem;
}

.stat-result {
  background: var(--neutral-100);
  padding: var(--space-md);
  border-radius: var(--radius-md);
  margin: var(--space-md) 0;
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary);
  border: 2px dashed var(--primary);
  min-height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  word-break: break-word;
}

.stat-btn {
  background: var(--neutral-100);
  border: 2px solid var(--primary);
  color: var(--primary);
  padding: var(--space-sm) var(--space-lg);
  border-radius: 50px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  width: 100%;
  margin: var(--space-xs) 0;
  min-height: 44px;
}

.stat-btn:hover {
  background: var(--primary);
  color: white;
  transform: scale(1.02);
}

.stat-btn.primary {
  background: var(--primary);
  color: white;
}

.stat-btn.primary:hover {
  background: var(--primary-dark);
}

.stat-formula {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-style: italic;
  margin-top: var(--space-xs);
  padding-top: var(--space-xs);
  border-top: 1px solid var(--neutral-300);
}

.all-stats {
  background: linear-gradient(145deg, var(--neutral-100), var(--surface-solid));
  border: 2px solid var(--primary);
}

.data-summary {
  background: var(--neutral-100);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-top: var(--space-lg);
  border: 1px solid var(--primary);
}

.data-summary h3 {
  color: var(--primary);
  margin-bottom: var(--space-lg);
  text-align: center;
}

.summary-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--space-md);
}

.summary-item {
  display: flex;
  justify-content: space-between;
  padding: var(--space-sm) var(--space-md);
  background: var(--surface-solid);
  border-radius: var(--radius-md);
  border: 1px solid var(--neutral-300);
}

.summary-label {
  font-weight: 600;
  color: var(--text-secondary);
}

.summary-value {
  font-weight: 700;
  color: var(--primary);
}


/* ===== FIXED: Scientific Calculator Mobile Layout - Maintain 5 Columns ===== */
@media (max-width: 768px) {
  /* Force scientific calculator to maintain 5 columns exactly like desktop */
  .sci-keypad,
  #scientific-calc .keypad,
  .keypad.sci-keypad {
    display: grid !important;
    grid-template-columns: repeat(5, 1fr) !important;
    gap: 4px;
    width: 100%;
  }
  
  /* Ensure all buttons stay in their grid cells */
  .sci-keypad .btn,
  #scientific-calc .keypad .btn,
  .keypad.sci-keypad .btn {
    width: 100%;
    min-width: 0;
    margin: 0;
    padding: 12px 2px;
    font-size: 0.9rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }
  
  /* Special handling for function button text */
  .sci-keypad .btn.fn,
  #scientific-calc .keypad .btn.fn {
    font-size: 0.8rem;
    padding: 12px 1px;
  }
  
  /* Ensure the grid doesn't break on very small screens */
  @media (max-width: 480px) {
    .sci-keypad .btn {
      font-size: 0.8rem;
      padding: 10px 1px;
    }
    
    .sci-keypad .btn.fn {
      font-size: 0.7rem;
    }
  }
  
  @media (max-width: 360px) {
    .sci-keypad .btn {
      font-size: 0.7rem;
      padding: 8px 1px;
    }
  }
}

/* Also fix basic calculator if needed (4 columns) */
@media (max-width: 768px) {
  #basic-calc .keypad {
    display: grid !important;
    grid-template-columns: repeat(4, 1fr) !important;
    gap: 4px;
  }
  
  #basic-calc .keypad .btn {
    width: 100%;
    padding: 12px 2px;
    font-size: 1rem;
  }
}

/* Matrix Calculator */
.matrix-dimension-panel {
  background: var(--neutral-100);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin-bottom: var(--space-xl);
  border: 1px solid var(--neutral-300);
}

.dimension-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-end;
  gap: var(--space-xl);
  justify-content: center;
}

.dimension-box {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-xs);
}

.dimension-box label {
  font-weight: 600;
  color: var(--primary);
  text-transform: uppercase;
  font-size: 0.9rem;
  letter-spacing: 1px;
}

.dimension-selector {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  background: var(--surface-solid);
  padding: var(--space-xs) var(--space-md);
  border-radius: 50px;
  border: 2px solid var(--primary);
}

.dim-select {
  width: 70px;
  padding: var(--space-xs);
  border: none;
  background: transparent;
  color: var(--text-primary);
  font-size: 1.1rem;
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  border-radius: var(--radius-sm);
}

.dim-select:hover {
  background: var(--neutral-300);
}

.dimension-selector span {
  font-size: 1.3rem;
  font-weight: 700;
  color: var(--primary);
}

.matrices-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-xl);
  margin-bottom: var(--space-xl);
}

.matrix-structure {
  background: var(--surface-solid);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  box-shadow: var(--shadow);
}

.matrix-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--space-md);
  padding: 0 var(--space-xs);
}

.matrix-header h3 {
  margin: 0;
  color: var(--text-primary);
}

.matrix-badge {
  background: var(--primary);
  color: white;
  padding: var(--space-xs) var(--space-md);
  border-radius: 30px;
  font-size: 0.9rem;
  font-weight: 600;
}

.matrix-brackets {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
}

.matrix-left-bracket,
.matrix-right-bracket {
  font-size: 4rem;
  line-height: 1;
  color: var(--primary);
  font-family: monospace;
  opacity: 0.8;
}

.matrix-grid {
  display: inline-grid;
  gap: var(--space-xs);
  padding: var(--space-sm);
  background: var(--neutral-100);
  border-radius: var(--radius-md);
}

.matrix-grid input {
  width: 70px;
  height: 60px;
  text-align: center;
  font-size: 1.1rem;
  font-weight: 500;
  border: 2px solid var(--neutral-300);
  border-radius: var(--radius-md);
  background: var(--surface-solid);
  color: var(--text-primary);
  transition: all 0.2s;
}

.matrix-grid input:focus {
  border-color: var(--primary);
  outline: none;
  box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
  transform: scale(1.02);
}

.result-grid {
  background: var(--primary-light, #f0f3ff);
}

.result-grid span {
  width: 70px;
  height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--surface-solid);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 1.1rem;
  color: var(--primary);
  border: 2px solid var(--primary);
}

.matrix-operations-panel {
  background: var(--neutral-100);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  margin: var(--space-xl) 0;
  border: 1px solid var(--neutral-300);
}

.matrix-operations-panel h3 {
  text-align: center;
  margin-bottom: var(--space-lg);
  color: var(--primary);
}

.operation-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-sm);
  justify-content: center;
}

.op-btn {
  background: var(--surface-solid);
  border: 2px solid var(--primary);
  color: var(--primary);
  padding: var(--space-sm) var(--space-lg);
  border-radius: 50px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-xs);
  font-size: 0.95rem;
  min-height: 44px;
}

.op-btn:hover {
  background: var(--primary);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(67, 97, 238, 0.3);
}

.matrix-result-panel {
  background: var(--surface-solid);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  text-align: center;
  border: 2px solid var(--primary);
  margin-top: var(--space-lg);
}

.matrix-result-panel h3 {
  margin-bottom: var(--space-lg);
  color: var(--primary);
}

.matrix-message {
  margin-top: var(--space-lg);
  padding: var(--space-sm);
  border-radius: var(--radius-md);
  font-weight: 500;
  text-align: center;
  background: var(--neutral-100);
  color: var(--text-primary);
  border-left: 4px solid var(--primary);
}

/* ===== 6. ANIMATIONS ===== */
@keyframes fadeSlide {
  from {
    opacity: 0;
    transform: translateY(15px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ===== 7. UTILITY CLASSES ===== */
:focus-visible {
  outline: 3px solid var(--primary);
  outline-offset: 2px;
}

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

/* ===== 8. RESPONSIVE DESIGN (SINGLE MOBILE MEDIA QUERY) ===== */
@media (max-width: 768px) {
  /* Show mobile menu button */
  .mobile-menu {
    display: block;
  }
  
  /* App Layout - Stack vertically */
  .app-layout {
    flex-direction: column;
    padding: var(--space-sm);
    gap: var(--space-md);
  }
  
  /* Sidebar - Mobile Drawer (hidden by default) */
  .sidebar {
    position: fixed;
    left: -260px; /* Hidden off-screen */
    top: var(--navbar-height);
    width: 260px;
    height: calc(100vh - var(--navbar-height));
    z-index: 99;
    border-radius: 0;
    transition: left 0.3s ease; /* Smooth slide animation */
    padding-bottom: var(--space-lg);
    max-height: calc(100vh - var(--navbar-height));
    box-shadow: 2px 0 10px rgba(0, 0, 0, 0.1);
    background: var(--surface);
    backdrop-filter: blur(16px) saturate(180%);
  }
  
  /* When open class is added */
  .sidebar.open {
    left: 0; /* Slide in */
  }
  
  /* Overlay when sidebar is open (optional - can be added via JS) */
  body.sidebar-open::after {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    z-index: 98;
    backdrop-filter: blur(3px);
  }
  
  /* Sidebar navigation */
  .sidebar nav ul {
    padding-bottom: var(--space-xl);
  }
  
  /* Main Content - Full width */
  .main-content {
    padding: var(--space-md);
    margin-left: 0;
    width: 100%;
  }
  
  /* Navbar adjustments */
  .navbar {
    padding: var(--space-xs) var(--space-sm);
  }
  
  .logo h1 {
    font-size: 1rem;
  }
  
  .logo i {
    font-size: 1.5rem;
  }
  
  .nav-controls {
    gap: var(--space-xs);
  }
  
  /* Cards */
  .calc-card {
    padding: var(--space-md);
  }
  
  .calc-card h2 {
    font-size: 1.25rem;
    margin-bottom: var(--space-md);
  }
  
  /* Keypad */
  .keypad {
    gap: var(--space-xs);
  }
  
  .sci-keypad {
    grid-template-columns: repeat(4, 1fr);
  }
  
  .btn {
    padding: var(--space-sm) var(--space-xs);
    font-size: 1rem;
    min-height: 48px;
  }
  
  /* Advanced Grid */
  .advanced-grid {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }
  
  /* Statistics */
  .statistics-grid {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }
  
  .section-header {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .input-controls {
    width: 100%;
  }
  
  .action-btn.small,
  .reset-btn.small {
    flex: 1;
  }
  
  .number-fields-grid {
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
  }
  
  .input-summary {
    flex-direction: column;
    gap: var(--space-xs);
    text-align: center;
  }
  
  .summary-grid {
    grid-template-columns: 1fr;
  }
  
  /* Matrix */
  .matrices-container {
    grid-template-columns: 1fr;
    gap: var(--space-md);
  }
  
  .matrix-grid input,
  .result-grid span {
    width: 50px;
    height: 50px;
    font-size: 0.9rem;
  }
  
  .matrix-left-bracket,
  .matrix-right-bracket {
    font-size: 3rem;
  }
  
  .operation-buttons {
    flex-direction: column;
  }
  
  .op-btn {
    width: 100%;
  }
  
  .dimension-controls {
    flex-direction: column;
    gap: var(--space-md);
  }
  
  /* CGPA */
  .semester-header {
    flex-direction: column;
    align-items: flex-start;
  }
  
  .cgpa-metrics {
    flex-direction: column;
    gap: var(--space-md);
    padding: var(--space-md);
  }
  
  .metric {
    justify-content: space-between;
    width: 100%;
  }
  
  .cgpa-actions {
    flex-direction: column;
  }
  
  .action-btn,
  .reset-btn {
    width: 100%;
  }
  
  /* Input Groups */
  .input-group {
    flex-direction: column;
  }
  
  .input-group input {
    width: 100%;
  }
  
  /* Subject rows */
  .subject-row {
    flex-direction: column;
    align-items: stretch;
  }
  
  .subject-row .subject,
  .subject-row .credit,
  .subject-row .grade {
    width: 100%;
  }
  
  /* Chart */
  .chart-container {
    height: 180px;
  }
  
  .chart-container canvas {
    width: 100% !important;
    height: 100% !important;
  }
  
  /* Body text */
  body {
    font-size: 14px;
  }
  
  /* Buttons */
  .icon-btn {
    min-width: 40px;
    min-height: 40px;
    font-size: 1.2rem;
  }
}

/* Small Mobile Devices (under 400px) */
@media (max-width: 400px) {
  .number-fields-grid {
    grid-template-columns: repeat(2, 1fr);
  }
  
  .btn {
    font-size: 0.9rem;
    min-height: 44px;
  }
  
  .matrix-grid input,
  .result-grid span {
    width: 45px;
    height: 45px;
    font-size: 0.85rem;
  }
  
  .logo h1 {
    font-size: 0.9rem;
  }
  
  .sidebar {
    width: 240px;
    left: -240px;
  }
}

.seo-heading {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin: 20px 40px;
}

.seo-heading h1 {
  font-size: 26px;
  margin: 0;
}

.seo-heading h2 {
  font-size: 16px;
  font-weight: normal;
  color: gray;
  margin: 0;
}
@media (max-width: 600px) {
  .seo-heading {
    flex-direction: column;
    text-align: center;
    gap: 5px;
  }
}

/* ===== FIXED: Mobile Button Layout - Preserve Desktop Order ===== */
@media (max-width: 768px) {
  /* Scientific calculator - maintain 5x4 grid on mobile */
  .sci-keypad {
    display: grid;
    grid-template-columns: repeat(5, 1fr) !important;
    gap: 4px;
  }
  
  /* Ensure all scientific buttons stay in correct order */
  .sci-keypad .btn {
    font-size: 0.9rem;
    padding: 10px 2px;
  }
  
  /* Basic calculator - maintain 4x5 grid */
  #basic-calc .keypad {
    display: grid;
    grid-template-columns: repeat(4, 1fr) !important;
  }
  
  /* Prevent button reordering */
  .keypad, 
  .sci-keypad {
    display: grid !important;
  }
  
  /* Ensure proper button sizing */
  .btn {
    width: 100%;
    min-width: 0;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }
  
  /* Special handling for function buttons with text */
  .sci-keypad .btn.fn {
    font-size: 0.8rem;
    padding: 8px 2px;
  }
  
  /* Make sure the grid doesn't break */
  .keypad,
  .sci-keypad {
    grid-auto-flow: row;
  }
}

/* Extra small devices */
@media (max-width: 480px) {
  .sci-keypad .btn {
    font-size: 0.8rem;
    padding: 8px 1px;
  }
  
  .sci-keypad .btn.fn {
    font-size: 0.7rem;
  }
}

/* ===== FIXED: Basic Calculator Layout - 4 Columns ===== */

/* Desktop layout */
#basic-calc .keypad,
.basic-keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-bottom: var(--space-md);
}

/* Ensure buttons are properly sized */
#basic-calc .keypad .btn,
.basic-keypad .btn {
  width: 100%;
  min-width: 0;
  padding: 16px 8px;
  font-size: 1.2rem;
  margin: 0;
}

/* Mobile layout - maintain same 4 columns */
@media (max-width: 768px) {
  #basic-calc .keypad,
  .basic-keypad {
    display: grid !important;
    grid-template-columns: repeat(4, 1fr) !important;
    gap: 4px;
  }
  
  #basic-calc .keypad .btn,
  .basic-keypad .btn {
    padding: 12px 4px;
    font-size: 1rem;
  }
  
  /* Ensure the clear button text fits */
  #basic-calc .keypad .btn.reset,
  .basic-keypad .btn.reset {
    font-size: 0.9rem;
  }
}

/* Extra small devices */
@media (max-width: 480px) {
  #basic-calc .keypad .btn,
  .basic-keypad .btn {
    padding: 10px 2px;
    font-size: 0.9rem;
  }
  
  #basic-calc .keypad .btn.reset,
  .basic-keypad .btn.reset {
    font-size: 0.8rem;
  }
}

/* Also ensure scientific calculator maintains 5 columns on mobile */
@media (max-width: 768px) {
  .sci-keypad,
  #scientific-calc .keypad {
    display: grid !important;
    grid-template-columns: repeat(5, 1fr) !important;
    gap: 4px;
  }
}

/* ================= Footer ================= */

.site-footer{
    margin-top:40px;
    padding:18px 10px;
    text-align:center;
    font-size:14px;
    color:#555;
    background:rgba(255,255,255,0.6);
    backdrop-filter:blur(10px);
    border-top:1px solid rgba(0,0,0,0.08);
}

.site-footer p{
    margin:0;
    line-height:1.6;
}

.site-footer a{
    color:#4361ee;
    text-decoration:none;
    font-weight:500;
    margin:0 6px;
    transition:all 0.25s ease;
}

.site-footer a:hover{
    color:#1b2fd3;
    text-decoration:underline;
}

/* Dark mode support */

body.dark-mode .site-footer{
    background:rgba(30,30,30,0.6);
    color:#ddd;
    border-top:1px solid rgba(255,255,255,0.1);
}

body.dark-mode .site-footer a{
    color:#7ea1ff;
}

body.dark-mode .site-footer a:hover{
    color:#9bb7ff;
}