body {
            font-family: 'Inter', sans-serif;
            background-color: #f0f2f5;
            color: #1c1e21;
            display: flex;
            flex-direction: column;
            min-height: 100vh;
        }
        .container-wrapper {
            flex-grow: 1;
            display: flex;
            justify-content: center;
            padding: 1rem;
        }
        .main-content-area {
            display: flex;
            flex-direction: column;
            width: 100%;
            max-width: 768px;
            background-color: #ffffff;
            box-shadow: 0 1px 3px rgba(0,0,0,0.06), 0 2px 8px rgba(0,0,0,0.03);
            border-radius: 0.75rem;
            overflow: hidden;
        }
        .header {
            display: flex;
            align-items: center;
            padding: 1rem;
            border-bottom: 1px solid #e5e7eb;
            background-color: #ffffff;
            position: sticky;
            top: 0;
            z-index: 10;
        }
        .messages-list-container {
            flex-grow: 1;
            overflow-y: auto;
            padding: 1rem;
        }
        .user-item {
            display: flex;
            align-items: center;
            padding: 0.75rem 1rem;
            border-radius: 0.5rem;
            margin-bottom: 0.5rem;
            cursor: pointer;
            transition: background-color 0.2s;
        }
        .user-item:hover {
            background-color: #f3f4f6;
        }
        .user-item img {
            width: 48px;
            height: 48px;
            border-radius: 50%;
            object-fit: cover;
            margin-right: 1rem;
        }
        .user-item .user-name {
            font-weight: 600;
            font-size: 1.125rem;
        }
        .chat-messages {
            flex-grow: 1;
            padding: 1rem;
            overflow-y: auto;
            display: flex;
            flex-direction: column;
            gap: 0.75rem;
        }
        .message-bubble {
            max-width: 80%;
            padding: 0.75rem 1rem;
            border-radius: 1.25rem; /* Rounded full for bubbles */
            word-wrap: break-word;
        }
        .message-incoming {
            background-color: #e5e7eb; /* gray-200 */
            align-self: flex-start;
            border-bottom-left-radius: 0.25rem; /* less rounded corner on bottom left */
        }
        .message-outgoing {
            background-color: #1877f2; /* primary-blue */
            color: white;
            align-self: flex-end;
            border-bottom-right-radius: 0.25rem; /* less rounded corner on bottom right */
        }
        .message-time {
            font-size: 0.75rem; /* text-xs */
            color: #6b7280; /* gray-500 */
            margin-top: 0.25rem;
        }
        .message-outgoing .message-time {
            color: rgba(255, 255, 255, 0.7);
        }
        .chat-input-area {
            display: flex;
            align-items: center;
            padding: 1rem;
            border-top: 1px solid #e5e7eb;
            background-color: #ffffff;
            position: sticky;
            bottom: 0;
            z-index: 10;
        }
        .chat-input {
            flex-grow: 1;
            padding: 0.75rem 1rem;
            border: 1px solid #d1d5db;
            border-radius: 1.5rem; /* Rounded full */
            outline: none;
            font-size: 1rem;
            margin-right: 0.5rem;
        }
        .chat-send-btn {
            background-color: #1877f2;
            color: white;
            padding: 0.75rem 1.25rem;
            border-radius: 1.5rem; /* Rounded full */
            font-weight: 600;
            cursor: pointer;
            transition: background-color 0.2s;
            display: flex;
            align-items: center;
            justify-content: center;
        }
        .chat-send-btn:hover {
            background-color: #166fe5;
        }
        .chat-send-btn:disabled {
            background-color: #90baf7; /* Lighter blue for disabled */
            cursor: not-allowed;
        }
        .profile-pic {
            width: 40px;
            height: 40px;
            border-radius: 50%;
            object-fit: cover;
            margin-right: 0.75rem;
        }
        .loading-spinner {
            border: 4px solid rgba(0, 0, 0, 0.1);
            border-top: 4px solid #1877f2;
            border-radius: 50%;
            width: 30px;
            height: 30px;
            animation: spin 1s linear infinite;
            margin: 20px auto;
        }
        @keyframes spin {
            0% { transform: rotate(0deg); }
            100% { transform: rotate(360deg); }
        }
        /* Messenger Auth Specific Styles */
        .messenger-auth-container {
            display: flex;
            flex-direction: column;
            align-items: center;
            justify-content: center;
            min-height: 100vh;
            background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
            color: white;
            padding: 2rem;
            text-align: center;
        }
        .messenger-auth-card {
            background-color: white;
            padding: 2.5rem;
            border-radius: 1rem;
            box-shadow: 0 10px 25px rgba(0,0,0,0.2);
            max-width: 400px;
            width: 100%;
            color: #1c1e21; /* Dark text for card content */
        }
        .messenger-auth-card .logo-img {
            height: 4rem;
            width: 4rem;
            border-radius: 50%;
            object-fit: cover;
            margin-bottom: 1.5rem;
            margin-left: auto;
            margin-right: auto;
        }
        .messenger-auth-card h2 {
            font-size: 2rem;
            font-weight: 700;
            margin-bottom: 1.5rem;
            color: #1877f2; /* primary-blue */
        }
        .messenger-auth-card input {
            width: 100%;
            padding: 0.75rem 1rem;
            border: 1px solid #d1d5db;
            border-radius: 0.5rem;
            margin-bottom: 1rem;
            font-size: 1rem;
            outline: none;
            transition: border-color 0.2s;
        }
        .messenger-auth-card input:focus {
            border-color: #1877f2;
        }
        .messenger-auth-card button {
            width: 100%;
            padding: 0.75rem 1.5rem;
            background-color: #1877f2;
            color: white;
            border-radius: 0.5rem;
            font-weight: 600;
            cursor: pointer;
            transition: background-color 0.2s;
        }
        .messenger-auth-card button:hover {
            background-color: #166fe5;
        }
        .messenger-auth-card .auth-toggle-text {
            color: #1877f2;
            cursor: pointer;
            font-weight: 500;
            margin-top: 1rem;
            display: inline-block;
        }
        .messenger-auth-card .error-message {
            color: #ef4444; /* red-500 */
            font-size: 0.875rem;
            margin-top: 0.5rem;
        }
        .messenger-auth-card .success-message {
            color: #22c55e; /* green-500 */
            font-size: 0.875rem;
            margin-top: 0.5rem;
        }
        .button-spinner {
            border: 2px solid rgba(255, 255, 255, 0.3);
            border-top: 2px solid #fff;
            border-radius: 50%;
            width: 16px;
            height: 16px;
            animation: spin 1s linear infinite;
            margin-right: 8px;
            display: inline-block;
            vertical-align: middle;
        }