:root {
    --paper-color: #E8F1F2;
    --ink-color: #2E5E6E;
    --accent-color: #3A7B8C;
    --shadow-color: rgba(0,0,0,0.1);
}

html, body {
    width: 100%;
    height: 100%;
    margin: 0;
    padding: 0;
    overflow-x: hidden;
}

body {
    font-family: "楷体", "STKaiti", serif;
    /*
     * 封面背景：主色为仿古宣纸色(#FFFEFC)，叠加渐变模拟水墨效果。
     * 若要使用图片背景，请取消下方注释并将 URL 替换为本地图片路径
     * （如 wsf.jpg 改名为 cover-bg.jpg，或下载自己喜欢的水墨背景图）。
     *
     * 注意：img.zcool.cn 域名有防盗链限制，直接用网络图片在本地 file://
     * 协议下会无法显示。建议使用本地图片，或在部署后使用相对路径图片。
     */
    background: var(--paper-color) fixed;
    /* background-image: url('cover-bg.jpg');  ← 如需图片背景，取消此行注释 */
    color: var(--ink-color);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    /* 水墨渐变叠加层（与背景图可二选一） */
    background-image:
        radial-gradient(ellipse at 20% 30%, rgba(200, 220, 240, 0.5) 0%, transparent 50%),
        radial-gradient(ellipse at 80% 70%, rgba(180, 200, 220, 0.4) 0%, transparent 45%),
        linear-gradient(160deg, #E8F1F2 0%, #D5E3E8 40%, #C8D8E0 100%);
    background-size: cover;
    background-attachment: fixed;
    background-blend-mode: normal;
    background-repeat: no-repeat;
    background-position: center;
}

.book-cover {
    width: 90%;
    max-width: 900px;
    min-height: 60vh;
    position: relative;
    transform-style: preserve-3d;
    transition: all 0.8s ease;
    display: flex;
    flex-direction: column;
    align-items: center;
}

/* ================================================================
   修复：翻书动画遮罩
   问题：rotateY(-150deg) 时露出翻转过程的空白背面。
   方案：在书封面前面增加一个 book-back 层，翻转时同步显示，
         用渐变模拟书页横截面的质感，让动画更真实。
   ================================================================ */
.book-back {
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 100%;
    border-radius: 8px;
    /* 默认隐藏，配合 .book-cover.opened 同步显示 */
    opacity: 0;
    pointer-events: none;
    /* 书页横截面质感：中间浅、两边略深的渐变 */
    background: linear-gradient(
        90deg,
        rgba(160,140,120,0.15) 0%,
        rgba(220,200,180,0.35) 15%,
        rgba(200,180,160,0.2) 50%,
        rgba(220,200,180,0.35) 85%,
        rgba(160,140,120,0.15) 100%
    );
    border: 1px solid rgba(180,160,140,0.3);
    box-shadow: 0 10px 25px rgba(0,0,0,0.08);
    z-index: 1;
    transition: opacity 0.05s;
}

.book-cover.opened ~ .book-back,
.book-cover.opened + .book-back {
    /* 与书封同步翻转过渡 */
}

.front-cover {
    background: rgba(232, 241, 242, 0.95);
    border: 1px solid #A3C4D2;
    box-shadow: 0 10px 25px var(--shadow-color);
    padding: 2rem;
    text-align: center;
    transform-origin: left center;
    backface-visibility: hidden;
    width: 100%;
    border-radius: 8px;
    display: flex;
    flex-direction: column;
    align-items: center;
    position: relative;
    z-index: 2;
}

.author-portrait {
    width: 200px;
    height: 250px;
    margin: 0 auto 1.5rem;
    background: url('wsf.webp') center/cover;
    border-radius: 50% 50% 50% 50% / 60% 60% 40% 40%;
    box-shadow: 0 5px 15px rgba(0,0,0,0.2);
    clip-path: ellipse(45% 50% at 50% 50%);
}

.open-book {
    display: inline-block;
    padding: 0.8rem 2.5rem;
    background: var(--accent-color);
    color: white;
    border-radius: 3px;
    font-size: 1rem;
    transition: all 0.3s;
    margin: 1.5rem 0;
    border: none;
    cursor: pointer;
    box-shadow: 0 4px 6px var(--shadow-color);
    font-family: "楷体", serif;
}

.open-book:hover {
    background: var(--ink-color);
    transform: translateY(-2px);
    box-shadow: 0 6px 8px var(--shadow-color);
}

/* ===== 移动端优先的布局样式 ===== */
.links-section {
    width: 100%;
    max-width: 400px;
    padding: 1.2rem;
    background: rgba(255, 255, 255, 0.88);
    border-radius: 8px;
    box-shadow: 0 3px 10px rgba(0,0,0,0.08);
    margin-top: 1.5rem;
    order: 3;
}

.friend-links-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    grid-gap: 0.8rem;
    text-align: center;
    margin: 0;
    padding: 0;
}

.friend-links-grid a {
    color: var(--accent-color);
    text-decoration: none;
    padding: 0.5rem 0.3rem;
    border-bottom: 1px dashed rgba(58, 123, 140, 0.4);
    transition: all 0.3s;
    font-size: 0.9rem;
}

.friend-links-grid a:hover {
    color: var(--ink-color);
    border-bottom-color: var(--ink-color);
}

.links-title {
    text-align: center;
    margin-bottom: 1rem;
    color: var(--accent-color);
    font-size: 1rem;
    letter-spacing: 1px;
}

/* ================================================================
   翻书动画：book-back 同步遮罩
   book-cover 翻转后，用 book-back 替代显示，消除空白背面。
   ================================================================ */
.book-cover.opened {
    transform: rotateY(-150deg);
    pointer-events: none;
}

/* 书封翻走后，书背立即显现（opacity 与 transform 同步） */
.book-cover.opened + .book-back,
.book-cover.opened ~ .book-back {
    opacity: 1;
    z-index: 3;
}

/* ===== 桌面端布局调整 ===== */
@media (min-width: 768px) {
    .front-cover {
        flex-direction: row;
        justify-content: space-between;
        align-items: center;
        padding: 2.5rem;
    }

    .author-portrait {
        width: 240px;
        height: 300px;
        margin: 0 2rem 0 0;
    }

    .links-section {
        max-width: 280px;
        margin-top: 0;
        order: 0;
    }

    .friend-links-grid {
        grid-template-columns: 1fr;
    }

    .open-book {
        padding: 1rem 3rem;
        font-size: 1.1rem;
        margin: 2rem 0;
    }
}

@media (min-width: 992px) {
    .author-portrait {
        width: 280px;
        height: 350px;
    }

    .links-section {
        max-width: 320px;
    }
}