/* ==========================================================================
   DebtApp - Modern Mobile-First Styles
   ========================================================================== */

/* CSS Variables */
:root {
    --primary: #4F46E5;
    --primary-dark: #4338CA;
    --secondary: #64748B;
    --success: #10B981;
    --danger: #EF4444;
    --warning: #F59E0B;
    --background: #F9FAFB;
    --surface: #FFFFFF;
    --text-primary: #111827;
    --text-secondary: #6B7280;
    --border: #E5E7EB;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1);
    --nav-height: 60px;
    --bottom-nav-height: 70px;
}

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

html, body {
    height: 100%;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    font-size: 16px;
    line-height: 1.5;
    color: var(--text-primary);
    background-color: var(--background);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

#app {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.main-content {
    flex: 1;
    padding-bottom: var(--bottom-nav-height);
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    margin: 0 0 1rem 0;
    font-weight: 600;
    line-height: 1.2;
    color: var(--text-primary);
}

h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }

p {
    margin: 0 0 1rem 0;
}

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

/* Navigation - Top */
.top-nav {
    position: sticky;
    top: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    box-shadow: var(--shadow);
    z-index: 100;
    height: var(--nav-height);
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    height: 100%;
    padding: 0 1rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
}

.nav-user {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-currency {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    background: var(--background);
    border-radius: 9999px;
}

.user-avatar {
    font-size: 1.5rem;
    text-decoration: none;
}

/* Navigation - Bottom */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--surface);
    border-top: 1px solid var(--border);
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.1);
    display: flex;
    justify-content: space-around;
    padding: 0.5rem 0;
    z-index: 100;
    height: var(--bottom-nav-height);
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.25rem;
    color: var(--text-secondary);
    text-decoration: none;
    flex: 1;
    transition: color 0.2s;
}

.nav-item:hover, .nav-item.active {
    color: var(--primary);
}

.nav-icon {
    font-size: 1.5rem;
}

.nav-label {
    font-size: 0.75rem;
    font-weight: 500;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: 0.5rem;
    cursor: pointer;
    text-decoration: none;
    transition: all 0.2s;
    white-space: nowrap;
}

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

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

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

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

.btn-block {
    width: 100%;
}

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

/* Forms */
.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text-primary);
}

.form-control {
    width: 100%;
    padding: 0.75rem 1rem;
    font-size: 1rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    background: var(--surface);
    color: var(--text-primary);
    transition: border-color 0.2s;
}

.form-control:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-control:disabled {
    background: var(--background);
    cursor: not-allowed;
}

textarea.form-control {
    resize: vertical;
    min-height: 100px;
}

select.form-control {
    cursor: pointer;
}

.form-row {
    display: flex;
    gap: 1rem;
}

.flex-1 {
    flex: 1;
}

/* Radio Buttons */
.radio-group {
    display: flex;
    gap: 1rem;
}

.radio-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
}

.radio-label input[type="radio"] {
    width: 1.25rem;
    height: 1.25rem;
    cursor: pointer;
}

/* Authentication Pages */
.auth-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
}

.auth-card {
    width: 100%;
    max-width: 400px;
    padding: 2rem;
    background: var(--surface);
    border-radius: 1rem;
    box-shadow: var(--shadow-lg);
}

.auth-title {
    text-align: center;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.auth-subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 2rem;
}

.auth-footer {
    margin-top: 1.5rem;
    text-align: center;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.auth-footer a {
    color: var(--primary);
    text-decoration: none;
    font-weight: 600;
}

/* Dashboard */
.dashboard-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem;
}

.dashboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.summary-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.summary-card {
    padding: 1.5rem;
    border-radius: 0.75rem;
    color: white;
}

.summary-card.green {
    background: linear-gradient(135deg, var(--success) 0%, #059669 100%);
}

.summary-card.red {
    background: linear-gradient(135deg, var(--danger) 0%, #DC2626 100%);
}

.summary-label {
    font-size: 0.875rem;
    opacity: 0.9;
    margin-bottom: 0.5rem;
}

.summary-amount {
    font-size: 1.5rem;
    font-weight: 700;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    overflow-x: auto;
}

.tab-btn {
    padding: 0.75rem 1.5rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    font-weight: 500;
    cursor: pointer;
    white-space: nowrap;
    transition: all 0.2s;
}

.tab-btn:hover {
    background: var(--background);
}

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

/* Debts Container */
.debts-container {
    display: grid;
    gap: 1rem;
}

.debt-card {
    background: var(--surface);
    border-radius: 0.75rem;
    padding: 1.25rem;
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.debt-card-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 0.75rem;
}

.debt-card-title {
    font-size: 1.125rem;
    font-weight: 600;
    margin: 0;
}

.debt-card-amount {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary);
}

.debt-card-meta {
    display: flex;
    gap: 0.75rem;
    font-size: 0.875rem;
    color: var(--text-secondary);
}

/* Loading Spinner */
.loading-spinner {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 3rem 1rem;
    gap: 1rem;
}

.spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* Empty State */
.empty-state {
    text-align: center;
    padding: 3rem 1rem;
}

.empty-icon {
    font-size: 4rem;
    margin-bottom: 1rem;
}

.empty-state h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.empty-state p {
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

/* Page Container */
.page-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 1rem;
}

.page-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.back-btn {
    font-size: 1.5rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.2s;
}

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

/* Debt Form */
.debt-form {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
}

.form-section {
    margin-top: 2rem;
    padding-top: 2rem;
    border-top: 1px solid var(--border);
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.payment-item {
    position: relative;
    padding: 1rem;
    background: var(--background);
    border-radius: 0.5rem;
    margin-bottom: 1rem;
}

.btn-remove-payment {
    position: absolute;
    top: 0.5rem;
    right: 0.5rem;
    width: 2rem;
    height: 2rem;
    background: var(--danger);
    color: white;
    border: none;
    border-radius: 50%;
    font-size: 1.25rem;
    cursor: pointer;
    line-height: 1;
}

/* Status Badge */
.status-badge {
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.875rem;
    font-weight: 600;
}

.status-badge.active {
    background: #DBEAFE;
    color: #1E40AF;
}

.status-badge.settled {
    background: #D1FAE5;
    color: #065F46;
}

/* Balance Card */
.balance-card {
    padding: 1rem;
    background: var(--background);
    border-radius: 0.5rem;
    margin-bottom: 0.75rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.balance-card.positive {
    border-left: 4px solid var(--success);
}

.balance-card.negative {
    border-left: 4px solid var(--danger);
}

/* Settlement Card */
.settlement-card {
    padding: 1rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    margin-bottom: 0.75rem;
}

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

.settlement-amount {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--primary);
}

.settlement-btn {
    margin-top: 0.75rem;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 1rem;
}

.modal-content {
    background: var(--surface);
    border-radius: 0.75rem;
    max-width: 500px;
    width: 100%;
    max-height: 90vh;
    overflow-y: auto;
    padding: 1.5rem;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-secondary);
}

/* Messages */
.error-message {
    padding: 0.75rem 1rem;
    background: #FEE2E2;
    color: #991B1B;
    border-radius: 0.5rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

.success-message {
    padding: 0.75rem 1rem;
    background: #D1FAE5;
    color: #065F46;
    border-radius: 0.5rem;
    margin-bottom: 1rem;
    font-size: 0.875rem;
}

/* Toast Notifications */
.toast-container {
    position: fixed;
    top: 1rem;
    right: 1rem;
    z-index: 2000;
}

.toast {
    background: var(--surface);
    padding: 1rem 1.5rem;
    border-radius: 0.5rem;
    box-shadow: var(--shadow-lg);
    margin-bottom: 0.5rem;
    animation: slideIn 0.3s ease;
}

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

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

/* Badge */
.badge {
    display: inline-block;
    padding: 0.25rem 0.5rem;
    background: var(--danger);
    color: white;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
    margin-left: 0.5rem;
}

/* Summary Box */
.summary-box {
    background: var(--background);
    padding: 1.5rem;
    border-radius: 0.5rem;
    margin-bottom: 1.5rem;
}

.summary-row {
    display: flex;
    justify-content: space-between;
    padding: 0.5rem 0;
    border-bottom: 1px solid var(--border);
}

.summary-row:last-child {
    border-bottom: none;
}

/* Settings Section */
.settings-section {
    background: var(--surface);
    padding: 1.5rem;
    border-radius: 0.75rem;
    box-shadow: var(--shadow);
    margin-bottom: 1.5rem;
}

/* Responsive Design */
@media (min-width: 768px) {
    .bottom-nav {
        display: none;
    }

    .main-content {
        padding-bottom: 0;
    }

    .debt-form, .settings-section {
        padding: 2rem;
    }
}

@media (max-width: 768px) {
    h1 { font-size: 1.5rem; }
    .auth-card { padding: 1.5rem; }
    .dashboard-header { flex-direction: column; gap: 1rem; align-items: flex-start; }
    .dashboard-header .btn { width: 100%; }
}

/* Friend Cards */
.friend-card, .request-card, .search-result-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 0.75rem;
    padding: 1rem;
    margin-bottom: 0.75rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    transition: box-shadow 0.2s;
}

.friend-card:hover, .request-card:hover, .search-result-card:hover {
    box-shadow: var(--shadow);
}

.friend-info {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex: 1;
}

.friend-avatar {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--background);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    flex-shrink: 0;
}

.friend-details {
    flex: 1;
    min-width: 0;
}

.friend-name {
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.friend-email {
    font-size: 0.875rem;
    color: var(--text-secondary);
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.request-actions {
    display: flex;
    gap: 0.5rem;
}

.search-result-action {
    flex-shrink: 0;
}

/* Tab Content */
.tab-content {
    display: none;
}

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

/* Friends List Specific */
#friendsList, #requestsList, #searchResults {
    margin-top: 1rem;
}

/* Search Results Container */
#searchResults {
    max-height: 400px;
    overflow-y: auto;
    margin-top: 1rem;
}

/* Mobile Responsive for Friend Cards */
@media (max-width: 480px) {
    .friend-card, .request-card, .search-result-card {
        flex-direction: column;
        align-items: flex-start;
    }

    .request-actions {
        width: 100%;
    }

    .request-actions .btn {
        flex: 1;
    }

    .search-result-action {
        width: 100%;
    }

    .search-result-action .btn {
        width: 100%;
    }
}

/* Group Cards */
.group-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 0.75rem;
    padding: 1rem;
    margin-bottom: 0.75rem;
    cursor: pointer;
    transition: all 0.2s;
}

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

.group-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
}

.group-info {
    display: flex;
    align-items: center;
    gap: 1rem;
    flex: 1;
}

.group-icon {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    flex-shrink: 0;
}

.group-details {
    flex: 1;
    min-width: 0;
}

.group-name {
    font-weight: 600;
    font-size: 1.125rem;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.group-meta {
    font-size: 0.875rem;
    color: var(--text-secondary);
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.group-arrow {
    font-size: 1.5rem;
    color: var(--text-secondary);
}

/* Member Cards */
.member-card {
    background: var(--background);
    border-radius: 0.5rem;
    padding: 1rem;
    margin-bottom: 0.75rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

/* Checkbox Label for Group Members */
.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem;
    border: 1px solid var(--border);
    border-radius: 0.5rem;
    margin-bottom: 0.5rem;
    cursor: pointer;
    transition: background 0.2s;
}

.checkbox-label:hover {
    background: var(--background);
}

.checkbox-label input[type="checkbox"] {
    width: 1.25rem;
    height: 1.25rem;
    cursor: pointer;
}

.checkbox-label span {
    font-weight: 500;
    color: var(--text-primary);
}

/* Groups List */
#groupsList, #groupMembersList {
    margin-top: 1rem;
}

#friendsCheckboxList {
    max-height: 300px;
    overflow-y: auto;
    margin-top: 0.5rem;
}