html {
    font-size: 100%; /* 16px */
}

body{
    color: #333;
    font-family: "M PLUS 1p";
}

a {
    text-decoration: none;
}


li{
    list-style: none;
    font-size: 1.1rem;
}


h1 {
    font-size: 2.4rem; 
    font-family: 'Monoton', serif;
}

/* header */
#header {
    max-width: 1340px;
    display: flex; /* 親要素に対してflexを当てると子要素が横並びになる */
    align-items: center;
    justify-content: space-between;
    margin: 0 auto;
    padding: 0 4%;
    height: 150px;
}

#header ul {
    display: flex;
    padding: 10px 0;
    align-items: center;
}

#header ul li {
    margin-left: 30px;
}

#header ul li a {
    color: #333;
    transition: all 0.3s;
}

#header ul li a:hover{
    opacity: 0.5;
    text-decoration: underline;
}

/* flexbox */
div.container{
    display: flex;
    justify-content: center;
    height: 700px;
    margin: 10px 0;
}

div.item-left{
    display: flex;
    flex-direction: column;
    margin: 0 5px;
    overflow-y: scroll;
    width: 10%;
}

div.item-left button{
    margin: 0 3px 3px;
    padding: 15px;
    color: #333;
    border: #333 1px solid;
    border-radius: 5px;
}

div.item-left button:hover{
    background-color: #f6f6f6;
}

div.item-right{
    aspect-ratio: 16 / 9;
    width: 70%;
}
iframe{
    width: 100%;
    height: 100%;
}

/* footer */
#footer {
    width: 80%;
    margin: 0 auto;
    padding: 10px 0;
    color: #999;
    border-top: 1px solid #dbdddf;
}

/* 携帯用 */
@media screen and (max-width: 900px){
    /* header */
    #header {
        flex-direction: column;
        height: auto;
        line-height: 40px;
        margin: 30px 0;
    }

    h1{
        font-size: 1.8rem;
    }

    #header li {
        font-size: 0.8rem;
        margin-top: 10px;
    }

    div.container{
        flex-direction: column;
        height: auto;
    }

    div.item-left{
        display: flex;
        flex-direction: row;
        flex-wrap: wrap;
        justify-content: center;
        margin-bottom: 6px;
        width: auto;
    }

    div.item-left button{
        margin: 2px;
        padding: 5px 10px;
    }

    div.item-right{
        margin: 0;
    }

    iframe{
        width: 100vw;
        height: 100vh;
    }

    #footer{
        width: 100%;
        text-align: center;
        padding: 10px;
    }
}


