/* ==========================================
   Split Expense Calculator - style.css
   Theme: Sleek Glassmorphism Dark
   ========================================== */

/* Variables */
:root {
  --font-main: 'Inter', 'Noto Sans TC', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  
  /* Color Palette */
  --bg-main: #0c081e;
  --bg-gradient: radial-gradient(circle at 50% 0%, #1a123a 0%, #0a0618 100%);
  
  --card-bg: rgba(26, 21, 48, 0.45);
  --card-bg-hover: rgba(35, 28, 64, 0.55);
  --card-border: rgba(255, 255, 255, 0.07);
  --card-border-focus: rgba(124, 58, 237, 0.4);
  
  --color-text-primary: #f3f4f6;
  --color-text-secondary: #9ca3af;
  --color-text-muted: #6b7280;
  
  /* Accent Colors */
  --primary: #8b5cf6;       /* Violet */
  --primary-hover: #7c3aed;
  --primary-light: rgba(139, 92, 246, 0.15);
  
  --success: #10b981;       /* Emerald */
  --success-hover: #059669;
  --success-light: rgba(16, 185, 129, 0.15);
  
  --danger: #ef4444;        /* Red */
  --danger-hover: #dc2626;
  --danger-light: rgba(239, 68, 68, 0.15);
  
  --warning: #f59e0b;       /* Amber */
  
  --input-bg: rgba(15, 11, 31, 0.6);
  --input-border: rgba(255, 255, 255, 0.1);
  --input-text: #f3f4f6;
  
  /* Shadow & Radii */
  --shadow-premium: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
  --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.2);
  --radius-lg: 16px;
  --radius-md: 10px;
  --radius-sm: 6px;
  
  /* Transitions */
  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
  font-family: var(--font-main);
  background: var(--bg-main);
  background-image: var(--bg-gradient);
  color: var(--color-text-primary);
  min-height: 100vh;
  line-height: 1.5;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* App Container Layout */
.app-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

/* Header */
.app-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.25rem 2rem;
  background: rgba(20, 15, 43, 0.6);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid var(--card-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-premium);
}

.header-logo {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.logo-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  background: linear-gradient(135deg, var(--primary) 0%, #a78bfa 100%);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  box-shadow: 0 4px 15px rgba(139, 92, 246, 0.4);
}

.logo-icon i {
  width: 24px;
  height: 24px;
}

.app-header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  background: linear-gradient(to right, #ffffff, #c084fc);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: -0.025em;
}

.app-header .subtitle {
  font-size: 0.85rem;
  color: var(--color-text-secondary);
}

/* Grid Layout */
.app-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}

.panel-left, .panel-right {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

/* Card Component */
.card {
  border-radius: var(--radius-lg);
  border: 1px solid var(--card-border);
  overflow: hidden;
  box-shadow: var(--shadow-premium);
  transition: transform var(--transition-normal), border-color var(--transition-normal);
}

.glass-card {
  background: var(--card-bg);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
}

.card:hover {
  background: var(--card-bg-hover);
}

.card-header {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid var(--card-border);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.card-title {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.card-title i {
  color: var(--primary);
  width: 20px;
  height: 20px;
}

.card-title h2 {
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--color-text-primary);
}

.card-body {
  padding: 1.5rem;
}

.scrollable-body {
  max-height: 480px;
  overflow-y: auto;
}

/* Disabled Card overlay effect */
.disabled-card {
  opacity: 0.45;
  pointer-events: none;
  filter: grayscale(40%);
  transition: opacity var(--transition-normal), filter var(--transition-normal);
}

.disabled-card:not(.disabled-card) {
  opacity: 1;
  pointer-events: auto;
  filter: none;
}

/* Badges */
.badge {
  font-size: 0.8rem;
  font-weight: 500;
  padding: 0.25rem 0.75rem;
  border-radius: 50px;
  background: var(--primary-light);
  color: #c084fc;
  border: 1px solid rgba(139, 92, 246, 0.3);
}

/* Form Controls */
.form-group {
  margin-bottom: 1.25rem;
}

.form-group:last-child {
  margin-bottom: 0;
}

.form-group-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

label {
  display: block;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: 0.5rem;
}

.input-group {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
}

input[type="text"],
input[type="number"],
select {
  width: 100%;
  padding: 0.75rem 1rem;
  background: var(--input-bg);
  border: 1px solid var(--input-border);
  border-radius: var(--radius-md);
  color: var(--input-text);
  font-family: var(--font-main);
  font-size: 0.95rem;
  outline: none;
  transition: all var(--transition-fast);
}

input:focus,
select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light);
}

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

/* Input Icon Wrapper */
.input-icon-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

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

.input-icon {
  position: absolute;
  left: 0.875rem;
  color: var(--color-text-muted);
  width: 18px;
  height: 18px;
  pointer-events: none;
}

/* Custom Select Wrapper */
.select-wrapper {
  position: relative;
}

.select-wrapper::after {
  content: '▼';
  font-size: 0.65rem;
  color: var(--color-text-muted);
  right: 1rem;
  top: 50%;
  transform: translateY(-50%);
  position: absolute;
  pointer-events: none;
}

select {
  appearance: none;
  -webkit-appearance: none;
  padding-right: 2.5rem;
  cursor: pointer;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  font-family: var(--font-main);
  font-size: 0.95rem;
  font-weight: 550;
  cursor: pointer;
  border: none;
  outline: none;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary) 0%, #7c3aed 100%);
  color: white;
  box-shadow: 0 4px 12px rgba(139, 92, 246, 0.25);
}

.btn-primary:hover {
  background: linear-gradient(135deg, #9a6eff 0%, #6d28d9 100%);
  transform: translateY(-1px);
}

.btn-success {
  background: linear-gradient(135deg, var(--success) 0%, #047857 100%);
  color: white;
  box-shadow: 0 4px 12px rgba(16, 185, 129, 0.25);
}

.btn-success:hover {
  background: linear-gradient(135deg, #34d399 0%, #065f46 100%);
  transform: translateY(-1px);
}

.btn-danger {
  background: linear-gradient(135deg, var(--danger) 0%, #b91c1c 100%);
  color: white;
  box-shadow: 0 4px 12px rgba(239, 68, 68, 0.2);
}

.btn-danger:hover {
  background: linear-gradient(135deg, #f87171 0%, #991b1b 100%);
  transform: translateY(-1px);
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.08);
  color: var(--color-text-primary);
  border: 1px solid rgba(255, 255, 255, 0.08);
}

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

.btn-full {
  width: 100%;
}

.btn-icon-text {
  padding: 0.6rem 1rem;
  font-size: 0.85rem;
}

.btn-text {
  background: none;
  border: none;
  color: var(--primary);
  font-size: 0.8rem;
  font-weight: 500;
  cursor: pointer;
  padding: 0.25rem 0.5rem;
  border-radius: var(--radius-sm);
  transition: background var(--transition-fast);
}

.btn-text:hover {
  background: var(--primary-light);
}

.btn:active, .btn-text:active {
  transform: scale(0.98);
}

.btn:disabled, .btn-text:disabled {
  opacity: 0.4;
  pointer-events: none;
}

/* Participant Badges List */
.participant-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  min-height: 80px;
  align-content: flex-start;
  padding: 0.75rem;
  background: rgba(0, 0, 0, 0.2);
  border-radius: var(--radius-md);
  border: 1px dashed var(--input-border);
}

.participant-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid rgba(255, 255, 255, 0.08);
  padding: 0.35rem 0.75rem;
  border-radius: 50px;
  font-size: 0.875rem;
  animation: popIn var(--transition-normal) forwards;
}

.participant-badge span {
  font-weight: 500;
}

.btn-remove-badge {
  background: none;
  border: none;
  color: var(--color-text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1px;
  border-radius: 50%;
  transition: all var(--transition-fast);
}

.btn-remove-badge:hover {
  color: var(--danger);
  background: var(--danger-light);
}

.btn-remove-badge i {
  width: 14px;
  height: 14px;
}

/* Checkbox Grid for Sharers */
.checkbox-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(110px, 1fr));
  gap: 0.5rem;
  padding: 0.75rem;
  background: rgba(0, 0, 0, 0.2);
  border-radius: var(--radius-md);
  border: 1px solid var(--input-border);
  max-height: 200px;
  overflow-y: auto;
}

.checkbox-label {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem;
  border-radius: var(--radius-sm);
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.04);
  cursor: pointer;
  user-select: none;
  font-size: 0.875rem;
  transition: all var(--transition-fast);
}

.checkbox-label:hover {
  background: rgba(255, 255, 255, 0.08);
}

.checkbox-label input[type="checkbox"] {
  accent-color: var(--primary);
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.checkbox-label.checked {
  background: rgba(139, 92, 246, 0.1);
  border-color: rgba(139, 92, 246, 0.3);
  color: #c084fc;
}

.empty-state-checkboxes {
  grid-column: 1 / -1;
  text-align: center;
  padding: 1rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
}

/* Empty States */
.empty-state {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 2.5rem 1rem;
  color: var(--color-text-muted);
  gap: 0.75rem;
  width: 100%;
}

.empty-icon {
  width: 36px;
  height: 36px;
  color: var(--color-text-muted);
  opacity: 0.6;
}

.empty-state p {
  font-size: 0.9rem;
}

/* Expense List Cards */
.expense-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.05);
  border-radius: var(--radius-md);
  margin-bottom: 0.75rem;
  animation: slideIn var(--transition-normal) forwards;
}

.expense-item:last-child {
  margin-bottom: 0;
}

.expense-info {
  display: flex;
  flex-direction: column;
  gap: 0.25rem;
}

.expense-title-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.expense-title {
  font-weight: 600;
  color: var(--color-text-primary);
  font-size: 0.95rem;
}

.expense-amount {
  font-weight: 700;
  color: #ffffff;
  font-size: 1.05rem;
}

.expense-details {
  font-size: 0.8rem;
  color: var(--color-text-secondary);
}

.expense-details span {
  color: #a78bfa;
  font-weight: 500;
}

.expense-sharers-badge {
  font-size: 0.75rem;
  color: var(--color-text-muted);
}

.btn-delete-expense {
  background: rgba(239, 68, 68, 0.1);
  color: var(--danger);
  border: 1px solid rgba(239, 68, 68, 0.2);
  width: 32px;
  height: 32px;
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-delete-expense:hover {
  background: var(--danger);
  color: white;
}

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

/* Tabs System */
.tabs-nav {
  display: flex;
  background: rgba(0, 0, 0, 0.2);
  border-radius: var(--radius-md);
  padding: 0.25rem;
  margin-bottom: 1.25rem;
  border: 1px solid var(--input-border);
}

.tab-btn {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  background: none;
  border: none;
  color: var(--color-text-secondary);
  padding: 0.6rem;
  font-size: 0.9rem;
  font-weight: 550;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

.tab-btn.active {
  background: rgba(255, 255, 255, 0.08);
  color: white;
  box-shadow: var(--shadow-inner);
}

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

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* Balances Tab UI */
.balances-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.balance-item {
  background: rgba(255, 255, 255, 0.02);
  border: 1px solid rgba(255, 255, 255, 0.04);
  border-radius: var(--radius-md);
  padding: 0.875rem 1rem;
}

.balance-user-info {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.balance-name {
  font-weight: 600;
  font-size: 0.95rem;
}

.balance-amount {
  font-weight: 700;
  font-size: 1rem;
}

.balance-amount.positive {
  color: var(--success);
}

.balance-amount.negative {
  color: var(--danger);
}

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

/* Meter/Bar */
.balance-bar-bg {
  height: 6px;
  background: rgba(255, 255, 255, 0.06);
  border-radius: 50px;
  overflow: hidden;
  position: relative;
}

.balance-bar-fill {
  height: 100%;
  border-radius: 50px;
  transition: width 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

.balance-bar-fill.positive {
  background: linear-gradient(to right, #34d399, var(--success));
}

.balance-bar-fill.negative {
  background: linear-gradient(to right, #f87171, var(--danger));
}

.balance-meta-text {
  font-size: 0.75rem;
  color: var(--color-text-muted);
  display: flex;
  justify-content: space-between;
  margin-top: 0.25rem;
}

/* Transfers Tab UI */
.transfers-list {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.transfer-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.05);
  border-radius: var(--radius-md);
  padding: 0.875rem 1.25rem;
  animation: popIn var(--transition-normal) forwards;
}

.transfer-actor {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.15rem;
  flex: 1;
}

.transfer-actor.debtor .name {
  color: #f87171;
  font-weight: 550;
}

.transfer-actor.creditor .name {
  color: #34d399;
  font-weight: 550;
}

.transfer-actor .role-tag {
  font-size: 0.7rem;
  color: var(--color-text-muted);
}

.transfer-flow {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.25rem;
  flex: 1.5;
  padding: 0 0.5rem;
}

.transfer-amount {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--warning);
}

.transfer-arrow-visual {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

.transfer-line {
  height: 1px;
  background: rgba(255, 255, 255, 0.1);
  width: 80%;
  position: absolute;
  top: 50%;
  z-index: 1;
}

.transfer-arrow-icon {
  background: rgba(15, 11, 31, 0.9);
  padding: 0.2rem;
  border-radius: 50%;
  border: 1px solid var(--input-border);
  z-index: 2;
  color: var(--warning);
}

.transfer-arrow-icon i {
  width: 14px;
  height: 14px;
  display: block;
}

.settlement-actions-hidden {
  display: none;
}

.settlement-actions-visible {
  display: block;
  margin-top: 1rem;
}

/* Modals */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(6, 4, 15, 0.8);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--transition-normal);
}

.modal-overlay.open {
  opacity: 1;
  pointer-events: auto;
}

.modal-card {
  width: 90%;
  max-width: 420px;
  border-radius: var(--radius-lg);
  border: 1px solid rgba(255, 255, 255, 0.1);
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.5);
  transform: translateY(20px);
  transition: transform var(--transition-normal);
  background: rgba(24, 18, 48, 0.95);
}

.modal-overlay.open .modal-card {
  transform: translateY(0);
}

.modal-header {
  padding: 1.5rem;
  border-bottom: 1px solid var(--card-border);
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.modal-header h3 {
  font-size: 1.15rem;
  font-weight: 600;
}

.warning-icon {
  color: var(--danger);
  width: 24px;
  height: 24px;
}

.modal-body {
  padding: 1.5rem;
  color: var(--color-text-secondary);
  font-size: 0.95rem;
}

.modal-footer {
  padding: 1.25rem 1.5rem;
  border-top: 1px solid var(--card-border);
  display: flex;
  justify-content: flex-end;
  gap: 0.75rem;
}

/* Toast System */
.toast-container {
  position: fixed;
  bottom: 1.5rem;
  right: 1.5rem;
  z-index: 1000;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  pointer-events: none;
}

.toast {
  background: rgba(20, 15, 43, 0.9);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border: 1px solid var(--card-border);
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-premium);
  display: flex;
  align-items: center;
  gap: 0.50rem;
  color: white;
  font-size: 0.9rem;
  animation: slideInLeft 0.3s cubic-bezier(0.4, 0, 0.2, 1) forwards;
  pointer-events: auto;
}

.toast-info i { color: var(--primary); }
.toast-success i { color: var(--success); }
.toast-error i { color: var(--danger); }

/* Keyframe Animations */
@keyframes popIn {
  from {
    transform: scale(0.9);
    opacity: 0;
  }
  to {
    transform: scale(1);
    opacity: 1;
  }
}

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

@keyframes slideInLeft {
  from {
    transform: translateX(100px);
    opacity: 0;
  }
  to {
    transform: translateX(0);
    opacity: 1;
  }
}

.animate-fade-in {
  animation: slideIn 0.5s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

.delay-100 { animation-delay: 0.1s; }
.delay-200 { animation-delay: 0.2s; }
.delay-300 { animation-delay: 0.3s; }

/* Responsive adjustments */
@media (max-width: 900px) {
  .app-grid {
    grid-template-columns: 1fr;
  }
  
  .app-container {
    padding: 1rem;
  }
}

@media (max-width: 480px) {
  .app-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 1rem;
    padding: 1rem;
  }
  
  #btn-reset {
    width: 100%;
  }

  .transfer-item {
    padding: 0.75rem;
  }
  
  .transfer-amount {
    font-size: 1rem;
  }
}