/* CSS Reset & Variables */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&display=swap');

:root {
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-card: rgba(255, 255, 255, 0.85);
    
    --primary: #4f46e5;
    --primary-hover: #4338ca;
    --primary-light: #e0e7ff;
    
    --success: #10b981;
    --success-light: #ecfdf5;
    --success-hover: #059669;
    
    --danger: #ef4444;
    --danger-light: #fef2f2;
    --danger-hover: #dc2626;

    --warning: #f59e0b;
    --warning-light: #fffbeb;

    --text-main: #0f172a;
    --text-muted: #64748b;
    --text-inverse: #ffffff;

    --border: rgba(226, 232, 240, 0.8);
    --border-focus: #818cf8;
    
    --font-heading: 'Outfit', sans-serif;
    --font-body: 'Inter', sans-serif;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.04), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.03), 0 8px 10px -6px rgba(0, 0, 0, 0.03);
    
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-body);
    background-color: var(--bg-primary);
    background-image: 
        radial-gradient(at 0% 0%, rgba(99, 102, 241, 0.06) 0px, transparent 50%),
        radial-gradient(at 50% 0%, rgba(16, 185, 129, 0.04) 0px, transparent 50%),
        radial-gradient(at 100% 0%, rgba(239, 68, 68, 0.04) 0px, transparent 50%);
    background-attachment: fixed;
    color: var(--text-main);
    min-height: 100vh;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    display: flex;
    flex-direction: column;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-heading);
    color: var(--text-main);
    font-weight: 600;
}

/* Layout Elements */
header {
    background: rgba(255, 255, 255, 0.7);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: all 0.3s ease;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-family: var(--font-heading);
    font-weight: 800;
    font-size: 1.5rem;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
}

.logo-icon {
    background: var(--primary);
    color: white;
    width: 32px;
    height: 32px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    font-weight: 900;
}

.user-menu {
    display: flex;
    align-items: center;
    gap: 16px;
}

.user-info {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--text-muted);
}

.user-username {
    color: var(--text-main);
    font-weight: 600;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 18px;
    font-family: var(--font-body);
    font-size: 0.9rem;
    font-weight: 600;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    outline: none;
    text-decoration: none;
}

.btn-primary {
    background-color: var(--primary);
    color: var(--text-inverse);
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background-color: var(--bg-secondary);
    color: var(--text-main);
    border-color: var(--border);
    box-shadow: var(--shadow-sm);
}

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

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

.btn-danger:hover {
    background-color: var(--danger);
    color: var(--text-inverse);
}

.btn-success {
    background-color: var(--success);
    color: var(--text-inverse);
}

.btn-success:hover {
    background-color: var(--success-hover);
    transform: translateY(-1px);
}

.btn-sm {
    padding: 6px 12px;
    font-size: 0.8rem;
    border-radius: var(--radius-sm);
}

.btn-icon-only {
    padding: 8px;
    border-radius: 50%;
}

/* Cards & Layout */
main {
    flex: 1;
    max-width: 1200px;
    width: 100%;
    margin: 0 auto;
    padding: 32px 24px;
}

.card {
    background: var(--bg-card);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 24px;
    margin-bottom: 24px;
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

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

/* Grid systems */
.grid-2 {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 24px;
}

.grid-3 {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}

.grid-1-2 {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 24px;
}

@media (max-width: 768px) {
    .grid-2, .grid-3, .grid-1-2 {
        grid-template-columns: 1fr;
    }
}

/* Forms & Inputs */
.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 8px;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    font-family: var(--font-body);
    font-size: 0.95rem;
    color: var(--text-main);
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    outline: none;
    transition: all 0.2s ease;
}

.form-control:focus {
    border-color: var(--border-focus);
    box-shadow: 0 0 0 4px rgba(99, 102, 241, 0.12);
}

.form-control::placeholder {
    color: #a1a1aa;
}

/* Auth Screens Specific */
.auth-container {
    max-width: 420px;
    margin: 60px auto;
    width: 100%;
}

.auth-title {
    font-size: 2rem;
    font-weight: 800;
    text-align: center;
    margin-bottom: 8px;
    background: linear-gradient(135deg, var(--primary), #818cf8);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.auth-subtitle {
    text-align: center;
    color: var(--text-muted);
    margin-bottom: 32px;
    font-size: 0.95rem;
}

.auth-switch {
    text-align: center;
    margin-top: 16px;
    font-size: 0.9rem;
    color: var(--text-muted);
}

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

.auth-switch a:hover {
    text-decoration: underline;
}

/* Dashboard Elements */
.dashboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
}

.dashboard-title h2 {
    font-size: 1.8rem;
    font-weight: 800;
}

.dashboard-title p {
    color: var(--text-muted);
    font-size: 0.95rem;
}

.trips-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}

.trip-card {
    display: flex;
    flex-direction: column;
    height: 100%;
    cursor: pointer;
}

.trip-name {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--text-main);
}

.trip-description {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 20px;
    flex-grow: 1;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.trip-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid var(--border);
    padding-top: 16px;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.trip-members-count {
    display: flex;
    align-items: center;
    gap: 6px;
    font-weight: 500;
}

/* Trip Workspace */
.workspace-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 24px;
    border-bottom: 1px solid var(--border);
    padding-bottom: 20px;
}

.workspace-title-area {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

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

/* Members Section */
.members-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.member-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 14px;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
}

.member-name {
    font-weight: 600;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    gap: 8px;
}

.owner-badge {
    background-color: var(--primary-light);
    color: var(--primary);
    font-size: 0.75rem;
    font-weight: 700;
    padding: 2px 6px;
    border-radius: 4px;
    text-transform: uppercase;
}

/* Spending and Balances */
.spending-stat {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 16px;
    border-radius: var(--radius-md);
    margin-bottom: 12px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
}

.spending-user {
    font-weight: 600;
}

.spending-amount {
    font-family: var(--font-heading);
    font-weight: 700;
    font-size: 1.1rem;
}

.summary-card {
    text-align: center;
    padding: 20px;
    background: linear-gradient(135deg, var(--bg-secondary), var(--bg-primary));
}

.summary-label {
    font-size: 0.85rem;
    text-transform: uppercase;
    font-weight: 700;
    letter-spacing: 0.05em;
    color: var(--text-muted);
    margin-bottom: 4px;
}

.summary-value {
    font-family: var(--font-heading);
    font-size: 2rem;
    font-weight: 800;
    color: var(--primary);
}

/* Settlement list style */
.settlement-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-top: 16px;
}

.settlement-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    background-color: var(--success-light);
    border: 1px dashed var(--success);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
}

.settlement-party {
    font-weight: 600;
}

.settlement-party-debtor {
    color: var(--danger);
}

.settlement-party-creditor {
    color: var(--success-hover);
}

.settlement-arrow {
    color: var(--text-muted);
    font-size: 1.1rem;
    margin: 0 8px;
}

.settlement-amount {
    font-family: var(--font-heading);
    font-weight: 800;
    color: var(--success-hover);
}

/* Empty state settlements */
.settled-state {
    padding: 24px;
    text-align: center;
    color: var(--success-hover);
    background-color: var(--success-light);
    border: 1px solid var(--success);
    border-radius: var(--radius-md);
    font-weight: 600;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

/* Transactions list */
.transaction-list {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.transaction-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    transition: border-color 0.2s ease;
}

.transaction-item:hover {
    border-color: var(--border-focus);
}

.trans-desc {
    font-weight: 600;
    margin-bottom: 4px;
}

.trans-meta {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.trans-amount-area {
    display: flex;
    align-items: center;
    gap: 16px;
}

.trans-amount {
    font-family: var(--font-heading);
    font-size: 1.2rem;
    font-weight: 700;
}

/* Alerts and Notifications */
.alert {
    padding: 14px 18px;
    border-radius: var(--radius-md);
    margin-bottom: 20px;
    font-size: 0.9rem;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 8px;
    animation: fadeIn 0.3s ease-out;
}

.alert-success {
    background-color: var(--success-light);
    color: var(--success-hover);
    border: 1px solid rgba(16, 185, 129, 0.3);
}

.alert-danger {
    background-color: var(--danger-light);
    color: var(--danger-hover);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

/* Modal dialog */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15, 23, 42, 0.3);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.2s ease;
}

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

.modal {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border);
    box-shadow: var(--shadow-xl);
    width: 100%;
    max-width: 480px;
    padding: 24px;
    transform: scale(0.95);
    transition: transform 0.2s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.modal-overlay.active .modal {
    transform: scale(1);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.modal-title {
    font-size: 1.3rem;
    font-weight: 700;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--text-muted);
    cursor: pointer;
    line-height: 1;
}

.modal-close:hover {
    color: var(--text-main);
}

/* Utilities & Animations */
.hidden {
    display: none !important;
}

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

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

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

.text-center {
    text-align: center;
}

.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mt-8 { margin-top: 8px; }

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(4px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Loading Spinner */
.spinner {
    border: 3px solid rgba(79, 70, 229, 0.1);
    width: 24px;
    height: 24px;
    border-radius: 50%;
    border-left-color: var(--primary);
    animation: spin 0.8s linear infinite;
    display: inline-block;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Custom Scrollbars */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}