.back_text { --highlight-color: #ff756f66; /* 기본색 */
 background-image: linear-gradient(90deg, transparent 50%, var(--highlight-color) 0); background-size: 200%; background-position: 0%; transition: background-position 2s linear; display: inline; } 

 .back_text.on { background-position: -100%; transition: background-position 2s linear; } 

 .back_text.reset { background-position: 0%; transition: background-position 0s; }