html, body {
    overflow-x: hidden;
}

body {
    margin: 0;
    font-family: "Helvetica Neue",
      Arial,
      "Hiragino Kaku Gothic ProN",
      "Hiragino Sans",
      Meiryo,
      sans-serif;
}

.belt {
    display: block;
    font-size: 1.5rem;
    height: 3rem;
    line-height: 3rem;
    margin: 1rem 0 2rem 0;
    padding-left: 1rem;
    color: #fff;
    background-color: #026584;
    font-weight: bold;
}

h2.belt {
    margin: 6rem 0 2rem 0;
}

h3 {
    display: block;
    width: 100%;
    border-bottom: #026584 1px solid;
    font-weight: normal;
    font-size: 2rem;
    padding-left: 1rem;
}

p {
    padding: 0 1rem;
}

a.link {
    color: #026584;
    text-decoration: none;
}
a:visited.link {
    color: #026584;
    text-decoration: none;
}

.row {
    display: flex;
    justify-content: center;
}

.column {
    width: 50%;
}

.column-1_3 {
    width: 33.3%;
    text-align: right;
}

.column-2_3 {
    width: 66.7%;
}

#book-description {
    padding: 1rem;
    font-size: 2rem;
    padding: 1rem;
    white-space: nowrap;
}
#book-description div.em:nth-of-type(3),div.em:nth-of-type(6) {
    margin-top: 0.5rem;
    margin-bottom: 0;
}
#book-description div.em:nth-of-type(4),div.em:nth-of-type(7) {
    margin-top: 0;
    margin-bottom: 0.5rem;
}

#book-front img {
    width: 100%;
    max-width: 400px;
}

.em {
    font-weight: bolder;
    font-size: 4rem;
    color: #026584;
}
li.em {
    font-weight: normal;
    font-size: 2rem;
    color: #026584;
}

.button-container {
    display: block;
    width: 100%;
    text-align: center;
}

.buy-button {
    display: inline-block;
    width: 30%;
    min-width: 200px;
    height: 3rem;
    line-height: 3rem;
    margin: 2rem 0 1rem 0;
    text-align: center;
    color: #fff;
    background-color: #f90;
    border-radius: 10px;
    text-decoration: none;
    font-weight: bold;
}
.buy-button:hover {
    box-shadow: rgb(252, 225, 185) 5px 5px 0;
    translate: 0 -3px;
}

.buy-button:active {
    box-shadow: none;
    translate: 0 3px;
}

.youtube {
    width: 32%;
    aspect-ratio: 16 / 9;
    margin: auto 5px auto 5px;
}
.youtube iframe {
    width: 100%;
    height: 100%;
}

section {
    position: relative;
}

.float-left-15 {
    position: absolute;
    right: 3rem;
    rotate: 15deg;
}

.float-left-345 {
    position: absolute;
    right: 3rem;
    rotate: 345deg;
}

img.cloud-founding {
    width: 250px;
    top: -3rem;
    border: 1px solid #fff;
}
img.book1 {
    width: 150px;
    top: -6rem;
    border: 1px solid #fff;
}
img.book2 {
    width: 100px;
    top: -4rem;
    border: 1px solid #fff;
}

.message {
    background-color: #b3d0d9;
    border-radius: 15px;
    margin: 1rem 2rem;
    padding: 1rem;
}

.summary {
    background-color: #b3d0d9;
    margin: 1rem;
    padding: 1rem;
}

.toc {
    width: 98%;
    border: #b3d0d9 2px solid;
    margin-left: 1%;
    margin-right: 1%;
    margin-bottom: 2px;
}

.profile {
    width: 90%;
    max-width: 350px;
    margin: 1rem;
}

.footer {
    margin-top: 3rem;
    padding: 2rem 0;
    background-color: #b3d0d9;
    font-size: 0.8rem;
}
.footer ul {
    list-style: none;
    margin: 2rem auto 5rem auto;
}
.footer ul li {
    position: relative;
}
.footer ul li::before {
    position: absolute;
    top: 50%;
    left: -1rem;
    transform: translateY(-50%);
    width: 0;
    height: 0;
    border: 0.3rem solid transparent;
    border-left: 0.4rem solid #026584;
    content: "";
}

.decorative {
    font-family: "游明朝",
        "Yu Mincho",
        YuMincho,
        "Hiragino Mincho Pro",
        serif;
    color: #026584;
    font-size: 4rem;
    line-height: 5rem;
    margin-left: 1rem;
    white-space: nowrap;
}
.decorative::first-letter {
    font-size: 6rem;
}
.decorative:first-child {
    margin-top: 2rem;
}
.decorative:nth-child(2) {
    margin-bottom: 1rem;
}


@media (max-width: 991.98px) {
    .em {
        font-size: 3.5rem;
    }

    .row:has(.youtube) {
        display: block;
        width: 100%;
    }
    .youtube {
        width: 98%;
        margin-left: 1%;
        margin-right: 1%;
    }

    img.cloud-founding {
        width: 168px;
        top: -2rem;
    }
    img.book1 {
        width: 100px;
        top: -3rem;
    }
    img.book2 {
        width: 67px;
        top: -2rem;
    }
}

@media (max-width: 767.98px) {
    #book-description {
        font-size: 1.5rem;
    }

    .em {
        font-size: 2.5rem;
    }

    img.cloud-founding {
        width: 125px;
        right: 0;
        top: -1.5rem;
    }
    img.book1 {
        width: 75px;
        right: 2rem;
        top: -3rem;
    }
    img.book2 {
        width: 50px;
        right: 2rem;
        top: -1rem;
    }
}

@media (max-width: 575.98px) {
    .belt {
        font-size: 1rem;
    }
    .belt .small {
        font-size: 0.75rem;
    }
    
    h3 {
        font-size: 1rem;
    }

    p {
        font-size: 0.8rem;
        padding: 0 0.75rem;
    }
    
    #book-front {
        margin-right: 1rem;
    }
    #book-description {
        font-size: 0.9rem;
    }

    .em {
        font-size: 1.5rem;
    }
    .small {
        font-size: 1rem;
    }

    .author .small {
        font-size: 0.75rem;
    }

    .message {
        margin: 1rem;
    }

    .row:has(.profile) {
        display: block;
        width: 100%;
    }
    .profile {
        margin-bottom: -0.5rem;
    }
    .row:has(.profile) > .column-2_3 {
        width: 100%;
    } 
}

@media (max-width: 379.98px) {
    .author .small {
        font-size: 0.6rem;
    }

    .decorative {
        font-size: 3rem;
    }
    .decorative::first-letter {
        font-size: 4rem;
    }
    .decorative:first-child {
        margin-top: 1.5rem;
    }

    img.cloud-founding {
        width: 100px;
        right: -2rem;
        top: -1.75rem;
    }
    img.book1 {
        width: 75px;
        right: -0.5rem;
        top: -3rem;
    }
    img.book2 {
        width: 50px;
        right: -0.5rem;
        top: -1rem;
    }
}

@media (max-width: 299.98px) {
    #book-description {
        font-size: 0.6rem;
    }

    .em {
        font-size: 1rem;
    }

    img.cloud-founding {
        display: none;
        visibility: hidden;
    }
    img.book1 {
        display: none;
        visibility: hidden;
    }
    img.book2 {
        display: none;
        visibility: hidden;
    }
}

@media (min-width: 1000px) {
    .content {
        width: 1000px;
        margin-left: 1%;
    }

    .belt {
        padding-left: 1%;
    }

    img.cloud-founding {
        translate: -5% 0;
    }
    img.book1 {
        translate: -5% 0;
    }
    img.book2 {
        translate: -5% 0;
    }
}

@media (min-width: 1100px) {
    .content {
        margin-left: 2%;
    }

    .belt {
        padding-left: 2%;
    }

    img.cloud-founding {
        scale: 1.2;
        translate: -10% 0;
    }
    img.book1 {
        scale: 1.2;
        translate: -10% 0;
    }
    img.book2 {
        scale: 1.2;
        translate: -10% 0;
    }
}

@media (min-width: 1200px) {
    body {
        font-size: 120%;
    }
    .content {
        width: 1200px;
    }
    .belt {
        font-size: 120%;
        padding-top: 0.5rem;
        padding-bottom: 0.5rem;
    }
    .buy-button {
        font-size: 120%;
        padding-top: 0.5rem;
        padding-bottom: 0.5rem;
    }

    img.cloud-founding {
        scale: 1.4;
        translate: -20% 0;
    }
    img.book1 {
        scale: 1.4;
        translate: -20% 0;
    }
    img.book2 {
        scale: 1.4;
        translate: -20% 0;
    }
}

@media (min-width: 1400px) {
    body {
        font-size: 140%;
    }
    .content {
        width: 1400px;
    }
    .belt {
        font-size: 140%;
        padding-top: 0.6rem;
        padding-bottom: 0.6rem;
    }
    .buy-button {
        font-size: 140%;
        padding-top: 0.6rem;
        padding-bottom: 0.6rem;
    }

    #book-description {
        padding: 1.5rem;
        font-size: 3rem;
    }
    #book-description div.em:nth-of-type(3),div.em:nth-of-type(6) {
        margin-top: 0.75rem;
        margin-bottom: 0;
    }
    #book-description div.em:nth-of-type(4),div.em:nth-of-type(7) {
        margin-top: 0;
        margin-bottom: 0.75rem;
    }
    #book-description .em {
        font-size: 5.5rem;
    }
    
    #book-front img {
        max-width: 600px;
    }

    img.cloud-founding {
        right: 4%;
    }
    img.book1 {
        right: 4%;
    }
    img.book2 {
        right: 4%;
    }

    .footer {
        margin-top: 3rem;
        padding: 2rem 0;
        background-color: #b3d0d9;
        font-size: 1.25rem;
    }
    .decorative {
        font-size: 6rem;
    }
    .decorative::first-letter {
        font-size: 9rem;
    }
    .decorative:first-child {
        margin-top: 4rem;
        margin-bottom: 1.5rem;
    }
    .decorative:nth-child(2) {
        margin-bottom: 3rem;
    }
}

@media (min-width: 1600px) {
    body {
        font-size: 160%;
    }
    .content {
        width: 1600px;
    }
    .belt {
        font-size: 160%;
        padding-top: 1rem;
        padding-bottom: 1rem;
    }
    .buy-button {
        font-size: 160%;
        padding-top: 1rem;
        padding-bottom: 1rem;
    }

    img.cloud-founding {
        right: 8%;
    }
    img.book1 {
        right: 8%;
    }
    img.book2 {
        right: 8%;
    }
}

@media (min-width: 2200px) {
    img.cloud-founding {
        right: 12%;
    }
    img.book1 {
        right: 12%;
    }
    img.book2 {
        right: 12%;
    }
}

@media (min-width: 2400px) {
    img.cloud-founding {
        right: 16%;
    }
    img.book1 {
        right: 16%;
    }
    img.book2 {
        right: 16%;
    }
}

@media (min-width: 2600px) {
    img.cloud-founding {
        right: 24%;
    }
    img.book1 {
        right: 24%;
    }
    img.book2 {
        right: 24%;
    }
}

@media (min-width: 2800px) {
    img.cloud-founding {
        right: 32%;
    }
    img.book1 {
        right: 32%;
    }
    img.book2 {
        right: 32%;
    }
}

@media (min-width: 3000px) {
    img.cloud-founding {
        right: 40%;
    }
    img.book1 {
        right: 40%;
    }
    img.book2 {
        right: 40%;
    }
}

@media (min-width: 3200px) {
    body {
        font-size: 180%;
    }
    .content {
        width: 1800px;
    }
    .belt {
        font-size: 180%;
        padding-top: 2rem;
        padding-bottom: 2rem;
    }
    .buy-button {
        font-size: 160%;
        padding-top: 1.5rem;
        padding-bottom: 1.5rem;
    }

    #book-description {
        padding: 2rem;
        font-size: 4rem;
    }
    #book-description div.em:nth-of-type(3),div.em:nth-of-type(6) {
        margin-top: 1rem;
    }
    #book-description div.em:nth-of-type(4),div.em:nth-of-type(7) {
        margin-bottom: 1rem;
    }
    #book-description .em {
        font-size: 7rem;
    }

    .footer {
        font-size: 1.5rem;
    }
    .decorative {
        font-size: 8rem;
    }
    .decorative::first-letter {
        font-size: 12rem;
    }
    .decorative:first-child {
        margin-top: 4rem;
        margin-bottom: 4rem;
    }
    .decorative:nth-child(2) {
        margin-bottom: 4rem;
    }
    
    #book-front img {
        max-width: 800px;
    }

    img.cloud-founding {
        right: 42%;
    }
    img.book1 {
        right: 42%;
    }
    img.book2 {
        right: 42%;
    }
}

@media (min-width: 3400px) {
    img.cloud-founding {
        right: 44%;
    }
    img.book1 {
        right: 44%;
    }
    img.book2 {
        right: 44%;
    }
}

@media (min-width: 3600px) {
    img.cloud-founding {
        right: 46%;
    }
    img.book1 {
        right: 46%;
    }
    img.book2 {
        right: 46%;
    }
}

@media (min-width: 4000px) {
    img.cloud-founding {
        display: none;
        visibility: hidden;
    }
    img.book1 {
        display: none;
        visibility: hidden;
    }
    img.book2 {
        display: none;
        visibility: hidden;
    }
}