:root {
  --primary-color: #2196F3;
  --secondary-color: #FFC107;
  --success-color: #4CAF50;
  --danger-color: #F44336;
  --text-color: #333;
  --text-light: #666;
  --background-color: #f5f5f5;
  --card-background: #ffffff;
  --border-radius: 12px;
  --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: 'Poppins', sans-serif;
  background-color: var(--background-color);
  color: var(--text-color);
  line-height: 1.6;
  padding-bottom: 80px;
}

.app-container {
  max-width: 100%;
  margin: 0 auto;
  padding: 16px;
}

header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--background-color);
  padding: 16px;
  margin: -16px -16px 20px -16px;
  box-shadow: var(--shadow);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

h1 {
  font-size: 2rem;
  color: var(--primary-color);
  display: flex;
  align-items: center;
  gap: 10px;
}

/* Buttons */
.primary-btn {
  background-color: var(--primary-color);
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: transform 0.2s ease;
}

.primary-btn:hover {
  transform: translateY(-2px);
}

.secondary-btn {
  background-color: transparent;
  color: var(--text-color);
  border: 1px solid var(--text-light);
  padding: 12px 24px;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-weight: 500;
}

.danger-btn {
  background-color: var(--danger-color);
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: all 0.2s ease;
}

.danger-btn:hover {
  transform: translateY(-2px);
  background-color: #d32f2f;
}

.whatsapp-btn {
  background-color: #25D366;
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: transform 0.2s ease;
}

.whatsapp-btn:hover {
  transform: translateY(-2px);
  background-color: #128C7E;
}

.mercadopago-btn {
  background-color: #009EE3;
  color: white;
  border: none;
  padding: 12px 24px;
  border-radius: var(--border-radius);
  cursor: pointer;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: transform 0.2s ease;
}

.mercadopago-btn:hover {
  transform: translateY(-2px);
  background-color: #008acf;
}

/* Fixed Add Expense Button for Mobile */
.mobile-action-button {
  display: none;
  position: fixed;
  bottom: 20px;
  right: 20px;
  z-index: 1000;
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: var(--primary-color);
  color: white;
  border: none;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
  cursor: pointer;
  transition: transform 0.2s;
}

.mobile-action-button:active {
  transform: scale(0.95);
}

/* Dashboard */
.dashboard {
  display: grid;
  gap: 16px;
}

.balance-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
  gap: 12px;
}

.balance-card {
  background: var(--card-background);
  padding: 16px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
}

.summary-section {
  background: var(--card-background);
  padding: 24px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
}

.summary-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.summary-card {
  padding: 20px;
  border-radius: var(--border-radius);
  background: linear-gradient(135deg, var(--primary-color), #64B5F6);
  color: white;
}

.amount {
  font-size: 2rem;
  font-weight: 600;
  margin-top: 10px;
}

/* Expenses List */
.expenses-list {
  background: var(--card-background);
  padding: 24px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
}

.expense-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px;
  border-bottom: 1px solid var(--background-color);
}

/* Debts Section */
.debts-section {
  background: var(--card-background);
  padding: 24px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  margin-top: 24px;
}

.debt-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px;
  border-bottom: 1px solid var(--background-color);
}

.debt-amount {
  font-weight: 600;
  color: var(--primary-color);
}

.no-debts {
  text-align: center;
  color: var(--text-light);
  padding: 20px;
}

/* Participant Management */
.participant-management {
  margin-top: 24px;
  background: var(--card-background);
  padding: 24px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
}

.add-participant-form {
  display: flex;
  gap: 12px;
  margin-bottom: 20px;
}

.add-participant-form input {
  flex: 1;
}

/* Controls Section */
.controls-section {
  background: var(--card-background);
  padding: 24px;
  border-radius: var(--border-radius);
  box-shadow: var(--shadow);
  margin-top: 24px;
}

.controls-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

/* Modal */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: rgba(0, 0, 0, 0.5);
  z-index: 1000;
}

.modal-header {
  padding-bottom: 20px;
  margin-bottom: 24px;
  border-bottom: 1px solid var(--background-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 1;
}

.top-actions {
  display: flex;
  gap: 8px;
  align-items: center;
}

.top-actions .secondary-btn {
  padding: 8px;
  height: 40px;
  width: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--border-radius);
}

.top-actions .secondary-btn:hover {
  background-color: var(--background-color);
}

.modal-content {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  max-width: 100%;
  margin: 0;
  border-radius: var(--border-radius) var(--border-radius) 0 0;
  max-height: 90vh;
  overflow-y: auto;
  background: var(--card-background);
  padding: 24px;
  box-shadow: var(--shadow);
}

.participant-select-modal .modal-content {
  max-width: 400px;
  margin: 20vh auto;
  border-radius: var(--border-radius);
}

.form-group {
  margin-bottom: 24px;
  position: relative;
}

.form-group label {
  display: block;
  margin-bottom: 8px;
  font-weight: 500;
  color: var(--text-color);
}

.form-group input,
.form-group select {
  width: 100%;
  padding: 16px;
  border: 1px solid #e0e0e0;
  border-radius: var(--border-radius);
  font-size: 16px;
  background: white;
  transition: border-color 0.2s, box-shadow 0.2s;
}

.form-group input:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.1);
}

.form-group input[type="number"] {
  -moz-appearance: textfield;
}

.form-group input[type="number"]::-webkit-outer-spin-button,
.form-group input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.amount-input-wrapper {
  position: relative;
}

.amount-input-wrapper::before {
  content: "$";
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-light);
  font-size: 16px;
}

.amount-input-wrapper input {
  padding-left: 32px;
}

.participants-container {
  background: var(--background-color);
  border-radius: var(--border-radius);
  padding: 16px;
  max-height: 200px;
  overflow-y: auto;
}

.participant-checkbox {
  display: flex;
  align-items: center;
  padding: 12px;
  margin-bottom: 8px;
  background: white;
  border-radius: var(--border-radius);
  transition: transform 0.2s;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
}

.participant-checkbox:hover {
  transform: translateX(4px);
  background: var(--primary-color);
  color: white;
}

.participant-checkbox input[type="checkbox"] {
  width: 20px;
  height: 20px;
  margin-right: 12px;
  cursor: pointer;
  border: 2px solid var(--primary-color);
  border-radius: 4px;
}

.participant-checkbox label {
  margin: 0;
  cursor: pointer;
  flex: 1;
  font-weight: 500;
}

.modal-header h2 {
  font-size: 1.5rem;
  color: var(--text-color);
}

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

.form-actions button {
  padding: 12px 24px;
}

.expense-item, 
.debt-item {
  padding: 16px;
  min-height: 60px;
}

.participant-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px;
  min-height: 60px;
  background-color: var(--background-color);
  border-radius: var(--border-radius);
  margin-bottom: 8px;
}

.participant-item button {
  padding: 8px;
  color: var(--danger-color);
}

.participant-item button:hover {
  background-color: var(--danger-color);
  color: white;
}

#participantsList {
  margin-top: 20px;
}

.participant-select-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.participant-select-item {
  padding: 16px;
  background: var(--background-color);
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.participant-select-item:hover {
  background: var(--primary-color);
  color: white;
  transform: translateX(4px);
}

.participant-balance {
  font-weight: 600;
}

/* Responsive */
@media (max-width: 768px) {
  .desktop-new-expense {
    display: none;
  }

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

  header {
    flex-direction: row;
    text-align: left;
  }

  h1 {
    font-size: 1.5rem;
  }

  .summary-section,
  .debts-section,
  .participant-management,
  .expenses-list,
  .controls-section {
    padding: 16px;
  }

  .summary-cards {
    grid-template-columns: 1fr;
    gap: 12px;
  }

  .modal-header {
    padding-bottom: 16px;
    margin-bottom: 16px;
  }

  .top-actions {
    gap: 4px;
  }
  
  .top-actions .secondary-btn {
    height: 36px;
    width: 36px;
    padding: 6px;
  }

  .top-actions button {
    padding: 8px 12px;
  }
  
  /* Improve scroll experience */
  .modal-content {
    padding-bottom: 80px;
  }

  .participants-container {
    max-height: 180px;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }
  
  /* Better touch feedback */
  .primary-btn:active,
  .secondary-btn:active {
    opacity: 0.8;
  }
  
  .controls-buttons {
    display: grid;
    grid-template-columns: 1fr;
    gap: 8px;
  }
  
  .controls-buttons button {
    width: 100%;
  }
}

@media (max-width: 768px) {
  .modal-content {
    padding: 16px;
  }
  
  .form-group {
    margin-bottom: 20px;
  }
  
  .participants-container {
    max-height: 180px;
  }
  
  .participant-checkbox {
    padding: 14px;
    margin-bottom: 6px;
  }
}