/* 全体のリセットと基本設定 */
body {
    margin: 0;
    padding: 0;
    font-family: "Helvetica Neue", Arial, "Hiragino Kaku Gothic ProN", "Hiragino Sans", sans-serif;
    background-color: #f9f9f9;
    color: #333;
    line-height: 1.6;
}

header {
    text-align: center;
    padding: 20px 20px 10px;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 300;
    letter-spacing: 0.1em;
    margin-bottom: 10px;
}

header p {
    color: #888;
    font-size: 0.9rem;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
}

/* グリッドレイアウト */
.column-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

/* カードのデザイン */
.column-card {
    background: #fff;
    padding: 30px;
    border-radius: 4px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.05);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    cursor: pointer;
    position: relative;
}

.column-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

.date {
    font-size: 0.75rem;
    color: #bbb;
    letter-spacing: 0.05em;
}

.column-card h2 {
    font-size: 1.25rem;
    margin: 15px 0;
    color: #222;
}

.column-card p {
    font-size: 0.9rem;
    color: #666;
    margin-bottom: 20px;
}

.read-more {
    text-decoration: none;
    color: #333;
    font-weight: bold;
    font-size: 0.85rem;
    border-bottom: 1px solid #333;
    padding-bottom: 2px;
}

footer {
    text-align: center;
    padding: 60px 20px;
    font-size: 0.8rem;
    color: #aaa;
}

.back-button-container {
    margin: 50px 0;
    text-align: center;
}

.back-button {
    display: inline-flex;
    align-items: center;
    text-decoration: none;
    color: #888; /* 控えめなグレー */
    font-size: 0.8rem;
    font-weight: 300;
    letter-spacing: 0.2em;
    transition: all 0.4s ease;
    position: relative;
    padding: 10px 20px;
}

.back-button .arrow {
    margin-right: 10px;
    transition: transform 0.4s ease;
}

/* ホバー時の演出 */
.back-button:hover {
    color: #000; /* 文字を濃く */
}

.back-button:hover .arrow {
    transform: translateX(-8px); /* 矢印が左にひょこっと動く */
}

/* 控えめな下線アニメーション */
.back-button::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 1px;
    background: #333;
    transition: all 0.4s ease;
    transform: translateX(-50%);
}

.back-button:hover::after {
    width: 100%; /* 下線が中央から伸びる */
}