@media screen and (max-width: 750px) {

    #box_container_chat {
        min-width: 700px;
        height: 520px;
    }

    .container_chat {
        height: 500px;
    }

    .chat_config {
        max-width: 250px;
    }

    #container_send_message {
        margin-top: 2px;
    }

    #container_send {
        flex: .2;
    }

    #container_change_theme {
        top: 20px;
        right: 20px;
    }

}