details.spoiler {
    border: 1px solid #e0a800;
    border-left: 4px solid #e0a800;
    border-radius: 4px;
    margin: 1em 0;
    padding: 0;
    background: #fdf6e3;
}

details.spoiler > summary {
    background: #fceabb;
    border-bottom: 1px solid #e0a800;
    padding: 0.6em 1em;
    font-weight: bold;
    cursor: pointer;
    list-style: none;
    color: #664d03;
}

details.spoiler > summary::-webkit-details-marker {
    display: none;
}

details.spoiler > summary::before {
    content: "\25b6\00a0";
}

details.spoiler[open] > summary::before {
    content: "\25bc\00a0";
}

details.spoiler[open] > summary {
    border-bottom: 1px solid #e0a800;
}

details.spoiler > *:not(summary) {
    padding: 0 1em;
}