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

:root {
    --primary: #6366f1;
    --primary-dark: #4f46e5;
    --secondary: #64748b;
    --success: #10b981;
    --danger: #ef4444;
    --warning: #f59e0b;
    --bg: #f8fafc;
    --bg-dark: #1e293b;
    --text: #0f172a;
    --text-light: #64748b;
    --border: #e2e8f0;
    --card-bg: #ffffff;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
}

.screen {
    display: none;
}

.screen.active {
    display: block;
}

/* Login Screen */
#login-screen.active {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.login-container {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 12px;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1);
    width: 100%;
    max-width: 400px;
}

.logo {
    text-align: center;
    margin-bottom: 2rem;
}

.logo h1 {
    font-size: 2rem;
    color: var(--primary);
    margin-bottom: 0.5rem;
}

.logo p {
    color: var(--text-light);
}

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

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

.form-group input {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary);
}

.btn {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-primary {
    background: var(--primary);
    color: white;
    width: 100%;
}

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

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

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

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

.text-center {
    text-align: center;
    margin-top: 1rem;
}

.text-center a {
    color: var(--primary);
    text-decoration: none;
}

.error-message {
    background: #fee2e2;
    color: #991b1b;
    padding: 0.75rem;
    border-radius: 6px;
    margin-top: 1rem;
}

/* Dashboard */
.navbar {
    background: var(--card-bg);
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.nav-brand {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--primary);
}

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

.container {
    display: flex;
    min-height: calc(100vh - 64px);
}

.sidebar {
    width: 250px;
    background: var(--card-bg);
    border-right: 1px solid var(--border);
    padding: 1rem 0;
}

.sidebar-nav {
    display: flex;
    flex-direction: column;
}

.nav-item {
    padding: 0.75rem 1.5rem;
    color: var(--text);
    text-decoration: none;
    display: flex;
    align-items: center;
    gap: 0.75rem;
    transition: background 0.2s;
}

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

.nav-item.active {
    background: var(--bg);
    border-left: 3px solid var(--primary);
    color: var(--primary);
}

.main-content {
    flex: 1;
    padding: 2rem;
    overflow-y: auto;
}

.content-section {
    display: none;
}

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

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 2rem;
    margin-bottom: 1.5rem;
}

h2 {
    font-size: 1.5rem;
    margin-bottom: 1rem;
}

/* Stats Grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.5rem;
    margin-bottom: 2rem;
}

.stat-card {
    background: var(--card-bg);
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.stat-card h3 {
    font-size: 2rem;
    color: var(--primary);
    margin-bottom: 0.5rem;
}

.stat-card p {
    color: var(--text-light);
}

/* Tables */
.table-container {
    background: var(--card-bg);
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

table {
    width: 100%;
    border-collapse: collapse;
}

thead {
    background: var(--bg);
}

th {
    padding: 1rem;
    text-align: left;
    font-weight: 600;
    color: var(--text);
    border-bottom: 2px solid var(--border);
}

td {
    padding: 1rem;
    border-bottom: 1px solid var(--border);
}

tbody tr:hover {
    background: var(--bg);
}

/* Modals */
.modal-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}

.modal-overlay.active {
    display: flex;
}

.modal {
    background: var(--card-bg);
    border-radius: 12px;
    width: 90%;
    max-width: 500px;
    max-height: 90vh;
    overflow-y: auto;
}

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

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

.modal-body {
    padding: 1.5rem;
}

/* Filters */
.filters {
    display: flex;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.filters select {
    padding: 0.5rem;
    border: 1px solid var(--border);
    border-radius: 6px;
}

/* Billing Card */
.billing-card {
    background: var(--card-bg);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

/* Quick Actions */
.quick-actions {
    margin-top: 2rem;
}

.action-buttons {
    display: flex;
    gap: 1rem;
    flex-wrap: wrap;
}

/* Badges */
.badge {
    display: inline-block;
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.875rem;
    font-weight: 500;
}

.badge-success {
    background: #d1fae5;
    color: #065f46;
}

.badge-danger {
    background: #fee2e2;
    color: #991b1b;
}

.badge-warning {
    background: #fef3c7;
    color: #92400e;
}

/* Responsive */
@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        border-right: none;
        border-bottom: 1px solid var(--border);
    }

    .sidebar-nav {
        flex-direction: row;
        overflow-x: auto;
    }

    .nav-item {
        white-space: nowrap;
    }
}