* {
    box-sizing: border-box;
}

#gameCanvas {
    display: block;
    width: 100%;
    height: auto;
    cursor: pointer;
    touch-action: manipulation;
}

/* ===== ヘッダー ===== */
.header {
    justify-content: flex-start;
}

.header nav {
    margin-left: auto;
}

.header-link {
    font-size: 1.5rem;
}

/* ===== right-column ===== */
.right-column-header h2 {
    color: black;
}

/* ===== キャンバスエリア ===== */
.canvas-container {
    max-width: 480px;
    margin: 16px auto;
}

@media (max-width: 767px) {
    .canvas-container {
        width: 88vw;
    }
}

/* ===== 謝辞セクション ===== */
.acknowledgement {
    margin: 24px auto;
    padding: 20px 24px;
    max-width: 900px;
    background: #f0f4f8;
    border-radius: 8px;
    color: #333;
    line-height: 1.8;
}

.acknowledgement h3 {
    font-size: 1.1rem;
    font-weight: 700;
    margin-bottom: 8px;
    border-left: 4px solid #555;
    padding-left: 8px;
}

/* ===== シェアボタン ===== */
.share-wrap {
    text-align: center;
    margin: 16px 0;
}

.btn-x-share {
    display: inline-block;
    background: #000;
    color: #fff;
    text-decoration: none;
    padding: 10px 24px;
    border-radius: 20px;
    font-size: 1rem;
    white-space: nowrap;
}

.btn-x-share:hover {
    background: #333;
}

/* ===== スクリーンリーダー専用（視覚的に非表示） ===== */
.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ===== ゲーム説明セクション ===== */
.game-description {
    margin: 30px auto 0;
    padding: 0 20px 20px;
    max-width: 900px;
    color: #222;
}

.game-description-inner {
    display: flex;
    flex-wrap: wrap;
    gap: 20px;
}

.game-description article {
    flex: 1 1 240px;
    background: #f5f5f5;
    border-radius: 8px;
    padding: 16px 20px;
}

.game-description h2 {
    font-size: 1.2rem;
    font-weight: 700;
    margin-bottom: 10px;
    border-left: 4px solid #555;
    padding-left: 8px;
}

.game-description ul {
    padding-left: 1.4em;
    line-height: 1.7;
    font-size: 1.05rem;
}

/* ===== page-wrapper: main + right-column ===== */
.page-wrapper {
    display: flex;
    flex-wrap: wrap;
    align-items: flex-start;
}

@media (min-width: 768px) {
    .page-wrapper {
        flex-wrap: nowrap;
    }

    .page-wrapper > main {
        flex: 1 1 auto;
        min-width: 0;
    }

    .right-column {
        flex: 0 0 240px;
        width: 240px;
        align-self: flex-start;
    }
}

@media (min-width: 990px) {
    .right-column {
        flex: 0 0 280px;
        width: 280px;
    }
}