body.open_popup {
    overflow: hidden;
}

.bg_onetime_popup {
    position: fixed;
    top: 0px;
    left: 0px;
    z-index: 20;
    width: 100vw;
    height: 100vh;
    background-color: rgba(0, 0, 0, 0.5);
    opacity: 0;
    visibility: hidden;
    transition: 0.5s;
}

body.open_popup .bg_onetime_popup {
    opacity: 1;
    visibility: visible;
}

/* ポップアップのサイズ */
.onetime_popup {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translateX(-50%) translateY(-50%);
    width: 70%;
    max-width: 800px;
    min-width: 300px;
    background-color: #fff;
}

.onetime_popup_title {
    position: relative;
    padding: 20px 20px;
    margin: 0;
    background-color: #3388dd;
    color: #fff;
    font-size: 32px;
    text-align: center;
    line-height: 1;
}

.onetime_popup_title_close {
    position: absolute;
    top: 0;
    right: -1em;
    z-index: 20;
    padding: 4px 8px;
    color: #ffffff;
    cursor: pointer;
}

.onetime_popup_content {
    text-align: center;
    padding: 30px 30px 30px;
    border-radius: 2px;
    font-size: 1.5em;
    font-weight: bold;
    background: #fff;
    box-shadow: 0 0 30px rgba(0, 0, 0, .6);
}