.promotion-wrapper {
  width: 1000px;
  margin: 40px auto;
}

.promotion-header {
  background-color: #C63929; /* 赤帯 */
  color: #fff;
  text-align: center;
  font-size: 24px;
  font-weight: bold;
  padding: 15px 0;
  border-top-left-radius: 8px;
  border-top-right-radius: 8px;
}

.promotion-container {
  position: relative;
  padding: 40px 35px;
  display: flex;
  justify-content: flex-start;
  align-items: flex-start;
  flex-wrap: nowrap;
  gap: 40px;
  border-left: 3px solid #ccc;
  border-right: 3px solid #ccc;
  border-bottom: 4px solid #ccc;
  border-radius: 0 0 8px 8px; 
  z-index: 1;
}

/* 二重線の内側 */
.promotion-container::before {
  content: "";
  position: absolute;
  top:0;
  left: 3px;
  right: 3px;
  bottom: 3px;
  border-left: 2px solid #ccc;
  border-right: 2px solid #ccc;
  border-bottom: 2px solid #ccc;
  border-radius:0 0 6px 6px; 
  z-index: 0; /* 前面に配置 */
}


.promotion-left {
    flex: 1;
    min-width: 300px;
    display: flex;
    justify-content: center;
    align-items: center; /* 上下中央に配置 */
}

.book-image {
    max-width: 100%;
    height: auto;
    box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.2);
}

.promotion-right {
    flex: 2;
    min-width: 400px;
    text-align: left; /* 左揃え */
}

.promotion-right h3 {
    font-size: 22px;
    font-weight: bold;
}

.title-main {
    color: #8E9FAC; /* 本文タイトル色 */
}

.highlight {
    color: #EA3800; /* 「5つ」の色 */
    font-weight: bold;
}

.promotion-right p {
    font-size: 16px;
    margin: 10px 0;
}

.bonus-text {
    color: #EA3800;
    font-weight: bold;
    margin-top: 10px;
    margin-bottom: 10px;
}

.video-section {
    text-align: center; /* 動画とその前のタイトルを中央 */
    margin-top: 35px;
}

.author-comment {
    font-weight: bold;
    margin-bottom: 10px;
}

.video-wrapper {
    margin: 20px auto;
    width: 70%; /* YouTube 70% */
    position: relative;
    z-index: 1;
}

.video-wrapper iframe {
    width: 100%;
    aspect-ratio: 16/9;
    border: none;
}

.button-container {
    display: flex;
    justify-content: center; /* ボタン中央 */
    gap: 20px;
    margin-top: 20px;
    flex-wrap: wrap;
    position: relative;
    z-index: 10;
}

.btn {
    display: inline-block;
    padding: 6px 20px;
    background-color: #8E9FAC; /* ボタンの色 */
    color: #fff;
    text-decoration: none;
    border-radius: 5px;
    transition: background-color 0.3s ease;
    width: 180px;
    text-align: center;
}

.btn:hover {
    background-color: #476074;
}

@media screen and (max-width: 767px) {
    
    .promotion-wrapper {
        width:100% !important;
    }
    
    .promotion-container {
        margin: 0 auto;
        flex-direction: column; /* 縦並び */
        padding: 40px 20px;
    }
    .promotion-left, .promotion-right {
        width: 100%;
        min-width: unset;
    }
    
    .book-image {
        width: 80%;
    }
    
    .video-wrapper {
        width: 80%;
    }
}