/* ===== 基本設定 ===== */
body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    font-family: 'Hiragino Kaku Gothic ProN', 'メイリオ', Meiryo, sans-serif;
    overflow: hidden;
    color: white;
}

/* ===== 背景 ===== */
.background-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: url("../png/treetree.jpg"); /* 階層が変わったのでパスを修正 */
    background-size: cover;
    background-position: center;
    transform: scale(1.1);
    z-index: -1;
}