/* ============================================
   BILL SPLITTER - DESIGN SYSTEM
   ============================================ */

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

/* ============================================
   CSS VARIABLES - DESIGN TOKENS
   ============================================ */
:root {
  /* Color Palette - Vibrant Gradients */
  --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
  --accent-gradient: linear-gradient(135deg, #fa709a 0%, #fee140 100%);

  /* Solid Colors */
  --primary: #667eea;
  --primary-dark: #5568d3;
  --secondary: #f5576c;
  --success: #00f2fe;
  --warning: #fee140;

  /* Neutral Colors - Dark Theme */
  --bg-primary: #0f0f23;
  --bg-secondary: #1a1a2e;
  --bg-tertiary: #16213e;
  --bg-card: rgba(26, 26, 46, 0.6);
  --bg-glass: rgba(255, 255, 255, 0.05);

  /* Text Colors */
  --text-primary: #ffffff;
  --text-secondary: #b4b4c5;
  --text-muted: #7a7a8c;

  /* Borders & Dividers */
  --border-color: rgba(255, 255, 255, 0.1);
  --border-hover: rgba(255, 255, 255, 0.2);

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
  --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 20px rgba(102, 126, 234, 0.3);

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;

  /* Border Radius */
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;

  /* Transitions */
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

/* Animated Background */
body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background:
    radial-gradient(circle at 20% 50%, rgba(102, 126, 234, 0.1) 0%, transparent 50%),
    radial-gradient(circle at 80% 80%, rgba(118, 75, 162, 0.1) 0%, transparent 50%),
    radial-gradient(circle at 40% 20%, rgba(245, 87, 108, 0.05) 0%, transparent 50%);
  z-index: -1;
  animation: backgroundShift 15s ease infinite;
}

@keyframes backgroundShift {

  0%,
  100% {
    opacity: 1;
  }

  50% {
    opacity: 0.8;
  }
}

/* ============================================
   TYPOGRAPHY
   ============================================ */
h1,
h2,
h3,
h4,
h5,
h6 {
  font-weight: 600;
  line-height: 1.2;
  margin-bottom: var(--spacing-sm);
}

h1 {
  font-size: 2.5rem;
  background: var(--primary-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

h2 {
  font-size: 1.75rem;
}

h3 {
  font-size: 1.25rem;
}

p {
  margin-bottom: var(--spacing-sm);
}

/* ============================================
   LAYOUT CONTAINER
   ============================================ */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-lg);
}

/* ============================================
   HEADER
   ============================================ */
.header {
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

.header h1 {
  font-size: 3rem;
  margin-bottom: var(--spacing-sm);
  animation: fadeInDown 0.6s ease;
}

.header p {
  color: var(--text-secondary);
  font-size: 1.1rem;
  animation: fadeInUp 0.6s ease 0.2s both;
}

/* ============================================
   CARDS & GLASSMORPHISM
   ============================================ */
.card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
  box-shadow: var(--shadow-md);
  transition: all var(--transition-normal);
  animation: fadeIn 0.6s ease;
}

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

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--spacing-md);
  padding-bottom: var(--spacing-sm);
  border-bottom: 1px solid var(--border-color);
}

.card-title {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--text-primary);
}

/* ============================================
   BUTTONS
   ============================================ */
.btn {
  padding: 0.75rem 1.5rem;
  border: none;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 500;
  font-family: inherit;
  cursor: pointer;
  transition: all var(--transition-fast);
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  position: relative;
  overflow: hidden;
}

.btn::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 0;
  height: 0;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.1);
  transform: translate(-50%, -50%);
  transition: width 0.6s, height 0.6s;
}

.btn:hover::before {
  width: 300px;
  height: 300px;
}

.btn-primary {
  background: var(--primary-gradient);
  color: white;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
  transform: translateY(-2px);
}

.btn-primary:active {
  transform: translateY(0);
}

.btn-secondary {
  background: var(--bg-tertiary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

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

.btn-danger {
  background: var(--secondary-gradient);
  color: white;
  box-shadow: 0 4px 15px rgba(245, 87, 108, 0.4);
}

.btn-danger:hover {
  box-shadow: 0 6px 20px rgba(245, 87, 108, 0.6);
  transform: translateY(-2px);
}

.btn-small {
  padding: 0.5rem 1rem;
  font-size: 0.875rem;
}

.btn-icon {
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

/* ============================================
   FORM INPUTS
   ============================================ */
.input-group {
  margin-bottom: var(--spacing-md);
}

.input-label {
  display: block;
  margin-bottom: var(--spacing-xs);
  color: var(--text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
}

.input {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  color: var(--text-primary);
  font-size: 1rem;
  font-family: inherit;
  transition: all var(--transition-fast);
}

.input:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
}

.input::placeholder {
  color: var(--text-muted);
}

/* Input with Icon */
.input-with-icon {
  position: relative;
}

.input-with-icon .input {
  padding-left: 2.5rem;
}

.input-icon {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  pointer-events: none;
}

/* ============================================
   GRID LAYOUTS
   ============================================ */
.grid {
  display: grid;
  gap: var(--spacing-md);
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}

.flex {
  display: flex;
  gap: var(--spacing-sm);
}

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

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

/* ============================================
   ITEM LIST
   ============================================ */
.item-list {
  list-style: none;
}

.item {
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  margin-bottom: var(--spacing-sm);
  transition: all var(--transition-fast);
  animation: slideIn 0.3s ease;
}

.item:hover {
  border-color: var(--border-hover);
  transform: translateX(4px);
}

.item-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: var(--spacing-sm);
}

.item-name {
  font-weight: 500;
  font-size: 1.1rem;
}

.item-price {
  color: var(--success);
  font-weight: 600;
  font-size: 1.1rem;
}

.item-actions {
  display: flex;
  gap: var(--spacing-xs);
  margin-top: var(--spacing-sm);
}

/* ============================================
   PERSON CHIPS
   ============================================ */
.person-chips {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-bottom: var(--spacing-md);
}

.person-chip {
  padding: 0.5rem 1rem;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  font-size: 0.875rem;
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  transition: all var(--transition-fast);
  cursor: pointer;
}

.person-chip:hover {
  background: var(--bg-secondary);
  border-color: var(--border-hover);
}

.person-chip.selected {
  background: var(--primary-gradient);
  border-color: var(--primary);
  color: white;
}

.person-chip .remove-btn {
  background: none;
  border: none;
  color: inherit;
  cursor: pointer;
  padding: 0;
  font-size: 1.2rem;
  line-height: 1;
  opacity: 0.7;
  transition: opacity var(--transition-fast);
}

.person-chip .remove-btn:hover {
  opacity: 1;
}

/* ============================================
   SUMMARY CARDS
   ============================================ */
.summary-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.summary-card {
  background: var(--bg-card);
  backdrop-filter: blur(10px);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  position: relative;
  overflow: hidden;
  transition: all var(--transition-normal);
  animation: scaleIn 0.4s ease;
}

.summary-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 4px;
  background: var(--primary-gradient);
}

.summary-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.summary-person {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: var(--spacing-md);
}

.summary-breakdown {
  color: var(--text-secondary);
  font-size: 0.875rem;
  margin-bottom: var(--spacing-xs);
}

.summary-total {
  font-size: 2rem;
  font-weight: 700;
  background: var(--success-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-top: var(--spacing-sm);
}

/* ============================================
   BADGES
   ============================================ */
.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-xl);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.badge-primary {
  background: var(--primary-gradient);
  color: white;
}

.badge-success {
  background: var(--success-gradient);
  color: white;
}

/* ============================================
   ANIMATIONS
   ============================================ */
@keyframes fadeIn {
  from {
    opacity: 0;
  }

  to {
    opacity: 1;
  }
}

@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }

  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(-20px);
  }

  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.9);
  }

  to {
    opacity: 1;
    transform: scale(1);
  }
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */
@media (max-width: 768px) {
  .header h1 {
    font-size: 2rem;
  }

  .container {
    padding: var(--spacing-md);
  }

  .card {
    padding: var(--spacing-md);
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }

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

  .flex {
    flex-direction: column;
  }

  .card-header {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-sm);
  }
}

@media (max-width: 480px) {
  .header h1 {
    font-size: 1.75rem;
  }

  .header p {
    font-size: 1rem;
  }

  .btn {
    width: 100%;
    justify-content: center;
  }

  .summary-total {
    font-size: 1.5rem;
  }
}

/* ============================================
   UTILITY CLASSES
   ============================================ */
.text-center {
  text-align: center;
}

.text-muted {
  color: var(--text-muted);
}

.mb-0 {
  margin-bottom: 0;
}

.mb-1 {
  margin-bottom: var(--spacing-xs);
}

.mb-2 {
  margin-bottom: var(--spacing-sm);
}

.mb-3 {
  margin-bottom: var(--spacing-md);
}

.mb-4 {
  margin-bottom: var(--spacing-lg);
}

.mt-0 {
  margin-top: 0;
}

.mt-1 {
  margin-top: var(--spacing-xs);
}

.mt-2 {
  margin-top: var(--spacing-sm);
}

.mt-3 {
  margin-top: var(--spacing-md);
}

.mt-4 {
  margin-top: var(--spacing-lg);
}
/* ============================================
   RADIO BUTTON TOGGLE STYLES
   ============================================ */
.tip-type-toggle {
  display: inline-flex;
  background: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 0.25rem;
  gap: 0.25rem;
}

.tip-type-toggle label {
  position: relative;
  padding: 0.625rem 1.25rem;
  border-radius: var(--radius-md);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-normal);
  user-select: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.tip-type-toggle label:hover {
  color: var(--text-primary);
  background: var(--bg-secondary);
}

.tip-type-toggle input[type="radio"] {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}

.tip-type-toggle input[type="radio"]:checked + span {
  color: white;
}

.tip-type-toggle label:has(input[type="radio"]:checked) {
  background: var(--primary-gradient);
  color: white;
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
  transform: translateY(-1px);
}

.tip-type-toggle label:has(input[type="radio"]:checked)::before {
  content: '✓';
  margin-right: 0.25rem;
  font-weight: bold;
}