.article-fab-group {
        position: fixed;
        right: 1rem;
        bottom: 1rem;
        display: flex;
        flex-direction: column;
        gap: 0.6rem;
        z-index: 1000;
    }
    .article-fab {
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
        gap: 0.1rem;
        width: 3.4rem;
        height: 3.4rem;
        border: none;
        border-radius: 50%;
        background-color: var(--color-heading);
        color: #ffffff;
        cursor: pointer;
        box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2);
        transition: transform 0.15s ease, opacity 0.2s ease;
    }
    .article-fab:hover {
        transform: translateY(-2px);
    }
    .article-fab-icon {
        font-size: 1.1rem;
        line-height: 1;
    }
    .article-fab-label {
        font-size: 0.6rem;
        line-height: 1;
    }
    .article-fab[hidden] {
        display: none;
    }

    .article-nav-overlay {
        position: fixed;
        inset: 0;
        background-color: rgba(0, 0, 0, 0.4);
        z-index: 1001;
    }
    .article-nav-overlay[hidden] {
        display: none;
    }
    .article-nav-panel {
        position: fixed;
        right: 0;
        top: 0;
        bottom: 0;
        width: min(20rem, 85vw);
        background-color: var(--color-surface);
        box-shadow: -4px 0 16px rgba(0, 0, 0, 0.18);
        z-index: 1002;
        display: flex;
        flex-direction: column;
        overflow-y: auto;
    }
    .article-nav-panel[hidden] {
        display: none;
    }
    .article-nav-panel-header {
        display: flex;
        align-items: center;
        justify-content: space-between;
        padding: 1rem 1.25rem;
        font-weight: 600;
        color: var(--color-heading);
        border-bottom: 1px solid var(--color-border);
        position: sticky;
        top: 0;
        background-color: var(--color-surface);
    }
    .article-nav-close {
        border: none;
        background: none;
        font-size: 1.4rem;
        line-height: 1;
        color: var(--color-muted);
        cursor: pointer;
    }
    .article-nav-list {
        list-style: none;
        margin: 0;
        padding: 0.75rem 0;
    }
    .article-nav-item a {
        display: block;
        padding: 0.5rem 1.25rem;
        color: var(--color-text);
        text-decoration: none;
    }
    .article-nav-item a:hover {
        background-color: var(--color-label-bg);
    }
    .article-nav-level-3 a {
        padding-left: 2.25rem;
        font-size: 0.9rem;
        color: var(--color-muted);
    }

    /* マスキングテープ */
    .mask-tape {
        position: relative;
        display: inline;
        cursor: pointer;
        color: transparent;
        background-color: #e23b3b;
        background-image: linear-gradient(135deg, rgba(255, 255, 255, 0.18) 0%, rgba(0, 0, 0, 0.08) 100%);
        border-radius: 3px;
        padding: 0.05em 0.2em;
        box-shadow: inset 0 0 0 1px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.15);
        box-decoration-break: clone;
        -webkit-box-decoration-break: clone;
        user-select: none;
        -webkit-user-select: none;
        -webkit-tap-highlight-color: transparent;
        transition: background-color 0.25s ease, color 0.25s ease, box-shadow 0.25s ease;
    }
    .mask-tape::selection {
        background-color: transparent;
    }
    .mask-tape.revealed {
        color: inherit;
        background-color: transparent;
        background-image: none;
        box-shadow: none;
        cursor: default;
        user-select: auto;
        -webkit-user-select: auto;
    }

    .article-fab-reset {
        background-color: #e23b3b;
    }

    .article-fab-peel {
        background-color: #2f8f6b;
    }

    /* 良いねボタン */
    .article-like {
        margin: 2rem 0 0.5rem;
        text-align: center;
    }
    .article-like-button {
        display: inline-flex;
        align-items: center;
        gap: 0.5rem;
        padding: 0.6rem 1.5rem;
        border: 1px solid var(--color-border);
        border-radius: 999px;
        background-color: var(--color-surface);
        color: var(--color-text);
        font-size: 1rem;
        cursor: pointer;
        box-shadow: var(--shadow-sm);
        transition: transform 0.15s ease, border-color 0.2s ease;
    }
    .article-like-button:hover {
        transform: translateY(-1px);
    }
    .article-like-button.is-liked {
        border-color: #e23b3b;
        color: #e23b3b;
    }
    .article-like-button:disabled {
        opacity: 0.6;
        cursor: default;
    }
    .article-like-count {
        font-weight: bold;
    }
    .article-like-login {
        margin-top: 0.6rem;
        font-size: 0.85rem;
        color: var(--color-muted);
    }

    /* 記事内 学習カード */
    .article-flashcard {
        margin: 1.75rem 0;
    }
    .article-flashcard .fc-flip-card {
        max-width: 100%;
    }
    /* 高さは表裏の長い方に合わせてJSで確定。最低でも約3行分を確保する */
    .article-flashcard .fc-flip-inner {
        height: auto;
        min-height: 8rem;
    }
    .article-flashcard .fc-flip-face {
        padding: 20px 24px;
    }
    .article-flashcard .fc-face-text {
        font-size: 1.05rem;
        white-space: normal;
    }
    .article-flashcard .fc-face-text > :first-child {
        margin-top: 0;
    }
    .article-flashcard .fc-face-text > :last-child {
        margin-bottom: 0;
    }