.PageMenuDialog[open] {
    all: unset;
    position: fixed;
    top: 0;
    left: auto;
    right: 0;
    bottom: 0;
    width: 80%;
    max-width: 270px;
    background-color: #fff;
    overflow-x: hidden;
    overflow-y: auto;
    margin: 0;
    animation: ShowSidePanel .2s;
}

.PageMenuDialog .CloseButton {
    all: unset;
    position: absolute;
    top: 0;
    right: 0;
    font-size: 25px;
    margin: 10px 20px;
    cursor: pointer;
    padding: 10px;
    color: #777;
    /* この要素が最前面に表示されるように */
    z-index: 100;
}

.PageMenuDialog .MenuContent {
    padding: 90px 0px 20px 0px;
    position: absolute;
    inset: 0;
    display: grid;
}

@keyframes ShowSidePanel {
    from {
        transform: translateX(100%);
    }
    to {
        transform: translateX(0);
    }
}