:root {
    --primary-color: #007bff;
    --secondary-color: #6c757d;
    --success-color: #28a745;
    --danger-color: #dc3545;
    --warning-color: #ffc107;
    --dark-color: #343a40;
    --light-color: #f8f9fa;
    --border-color: #dee2e6;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f5f5f5;
    color: #333;
}

#app {
    min-height: 100vh;
}

/* Auth Styles */
.auth-container {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.auth-box {
    background: white;
    padding: 40px;
    border-radius: 10px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
    width: 100%;
    max-width: 400px;
}

.auth-box h1 {
    margin-bottom: 30px;
    text-align: center;
    color: var(--dark-color);
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
    color: var(--dark-color);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    font-size: 14px;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 5px rgba(0, 123, 255, 0.25);
}

.btn {
    width: 100%;
    padding: 10px;
    border: none;
    border-radius: 5px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

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

.btn-primary:hover {
    background-color: #0056b3;
}

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

.btn-secondary:hover {
    background-color: #545b62;
}

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

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

.btn-small {
    padding: 5px 10px;
    font-size: 12px;
}

.toggle-auth {
    text-align: center;
    margin-top: 20px;
    color: var(--secondary-color);
}

.toggle-auth button {
    background: none;
    border: none;
    color: var(--primary-color);
    cursor: pointer;
    text-decoration: underline;
}

.alert {
    padding: 10px 15px;
    border-radius: 5px;
    margin-bottom: 20px;
}

.alert-danger {
    background-color: #f8d7da;
    color: #721c24;
    border: 1px solid #f5c6cb;
}

.alert-success {
    background-color: #d4edda;
    color: #155724;
    border: 1px solid #c3e6cb;
}

/* Dashboard Layout */
.dashboard {
    display: grid;
    grid-template-columns: 250px 1fr;
    min-height: 100vh;
    background-color: #fff;
}

.sidebar {
    background-color: var(--dark-color);
    color: white;
    padding: 20px;
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
}

.sidebar h2 {
    margin-bottom: 20px;
    font-size: 18px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
    padding-bottom: 10px;
}

.nav-list {
    list-style: none;
}

.nav-item {
    margin-bottom: 10px;
}

.nav-link {
    display: block;
    padding: 10px 15px;
    color: white;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color 0.3s ease;
    cursor: pointer;
}

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

.main-content {
    padding: 20px;
    display: flex;
    flex-direction: column;
}

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

.user-info {
    display: flex;
    align-items: center;
    gap: 15px;
}

.logout-btn {
    padding: 8px 15px;
    background-color: var(--danger-color);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

/* Chat Interface */
.chat-container {
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: 20px;
    height: calc(100vh - 100px);
}

.contacts-panel {
    background-color: white;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    padding: 15px;
    overflow-y: auto;
}

.contacts-panel h3 {
    margin-bottom: 15px;
    font-size: 16px;
}

.contact-item {
    padding: 10px;
    margin-bottom: 10px;
    background-color: var(--light-color);
    border-radius: 5px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background-color 0.3s ease;
}

.contact-item:hover,
.contact-item.active {
    background-color: #e9ecef;
}

.online-indicator {
    display: inline-block;
    width: 8px;
    height: 8px;
    background-color: var(--success-color);
    border-radius: 50%;
}

.offline-indicator {
    background-color: var(--secondary-color);
}

.chat-panel {
    display: flex;
    flex-direction: column;
    background-color: white;
    border: 1px solid var(--border-color);
    border-radius: 5px;
}

.chat-messages {
    flex: 1;
    padding: 20px;
    overflow-y: auto;
    border-bottom: 1px solid var(--border-color);
}

.message {
    margin-bottom: 15px;
    display: flex;
    flex-direction: column;
    align-items: flex-start;
}

.message.sent {
    align-items: flex-end;
}

.message-bubble {
    background-color: var(--light-color);
    padding: 10px 15px;
    border-radius: 10px;
    max-width: 70%;
    word-wrap: break-word;
}

.message.sent .message-bubble {
    background-color: var(--primary-color);
    color: white;
}

.message-time {
    font-size: 12px;
    color: var(--secondary-color);
    margin-top: 5px;
}

.message-actions {
    margin-top: 5px;
    font-size: 12px;
}

.message-actions button {
    background: none;
    border: none;
    color: var(--primary-color);
    cursor: pointer;
    margin-right: 10px;
}

.typing-indicator {
    font-style: italic;
    color: var(--secondary-color);
    font-size: 13px;
}

.chat-input {
    padding: 20px;
    display: flex;
    gap: 10px;
}

.chat-input input {
    flex: 1;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    font-size: 14px;
}

.chat-input button {
    padding: 10px 20px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 5px;
    cursor: pointer;
}

/* Admin Panel */
.admin-panel {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
}

.panel-card {
    background-color: white;
    border: 1px solid var(--border-color);
    border-radius: 5px;
    padding: 20px;
}

.panel-card h3 {
    margin-bottom: 20px;
    font-size: 18px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 10px;
}

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

.table th {
    background-color: var(--light-color);
    padding: 10px;
    text-align: left;
    font-weight: 600;
    border-bottom: 1px solid var(--border-color);
}

.table td {
    padding: 10px;
    border-bottom: 1px solid var(--border-color);
}

.table tr:hover {
    background-color: var(--light-color);
}

.invite-tree {
    margin-top: 20px;
}

.tree-node {
    margin-left: 20px;
    padding: 10px;
    background-color: var(--light-color);
    border-radius: 5px;
    margin-bottom: 10px;
}

.tree-node h4 {
    margin-bottom: 5px;
}

.tree-node p {
    font-size: 13px;
    color: var(--secondary-color);
}

/* Responsive */
@media (max-width: 768px) {
    .dashboard {
        grid-template-columns: 1fr;
    }

    .sidebar {
        display: none;
    }

    .chat-container {
        grid-template-columns: 1fr;
        gap: 10px;
    }

    .contacts-panel {
        display: none;
    }

    .auth-box {
        margin: 20px;
    }

    .message-bubble {
        max-width: 90%;
    }
}

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

.modal.active {
    display: flex;
    justify-content: center;
    align-items: center;
}

.modal-content {
    background-color: white;
    padding: 30px;
    border-radius: 10px;
    width: 100%;
    max-width: 400px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
}

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

.modal-header h2 {
    margin: 0;
}

.close-btn {
    background: none;
    border: none;
    font-size: 24px;
    cursor: pointer;
    color: var(--secondary-color);
}

.loading {
    text-align: center;
    padding: 20px;
    color: var(--secondary-color);
}

.spinner {
    border: 4px solid var(--light-color);
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    width: 40px;
    height: 40px;
    animation: spin 1s linear infinite;
    margin: 0 auto 10px;
}

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