/* タブボタンのスタイル */
.activity-btn {
    padding: 10px 20px;
    border: none;
    background: #eee;
    cursor: pointer;
    border-radius: 5px;
    font-weight: bold;
    transition: 0.3s;
}

.activity-btn.active {
    background: var(--primary-color);
    color: white;
}

/* リスト項目のスタイル */
.activity-item {
    background: white;
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
    border-left: 4px solid var(--primary-color);
    animation: fadeIn 0.5s ease;
}

.activity-date {
    font-size: 0.85rem;
    color: #888;
    display: block;
    margin-bottom: 5px;
}

.activity-title {
    font-weight: bold;
    display: block;
    color: var(--text-color);
    margin-bottom: 5px;
}

.activity-author {
    font-size: 0.9rem;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}