.empty-demo p:empty {
    background-color: #ffebee;
    border: 2px dashed #f44336;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
}
.empty-demo p:empty::before {
    content: "This paragraph is empty";
    color: #f44336;
    font-style: italic;
}
.empty-demo p:not(:empty) {
    background-color: #e8f5e8;
    border: 2px solid #4caf50;
    padding: 10px;
}