#header {
    background-color:#777;
    color: #eee; /* テキストの色 */
    padding: 20px; /* 内部余白 */
    box-shadow: 0 3px 6px 2px rgba(0, 0, 0, 0.3); /* 影を追加 */
}

#container {
    padding: 20px;
}

h1.page-title{
    padding: 0 0 15px;
    font-size: 3rem;
    font-weight: 700;
}

.material-list{
        margin: 0 auto;
}


.material-list ul {
    list-style-type: none;
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    width: 1116px;
    margin: 0 auto;
}

.material-list ul li {
    margin: 15px;
    border: solid;
    border-color: slategray;
    box-shadow: 0 2px 6px 2px rgba(0, 0, 0, 0.3);
}

.material-list a{
    display: flex;
}

@keyframes rainbow {
    0% { color: red; }
    14% { color: orange; }
    28% { color: yellow; }
    42% { color: green; }
    57% { color: blue; }
    71% { color: indigo; }
    85% { color: violet; }
    100% { color: red; }
}

.rainbow-text {
    animation: rainbow 10s linear infinite;
    font-size: 20px;
    font-weight:500;
}