body{
    width: 90%;
    max-width: 1280px;
    margin: auto;
  	overflow-wrap: break-word;
}

summary {
   	cursor: pointer;
    transition: 0.3s;
}
summary {
    display: block;
}
summary::-webkit-details-marker {
 	display:none;
}

.r18{
    background: silver;
    width:95%;
    max-width:720px;
    padding: 10px;
    border-radius: 5px;
}
.toggle::after {
    content: "[R18関連リンク表示]";
}
details[open] .toggle::after {
    content: "[閉じる]";
}