/* ============================================================
   效果展示水印 · 仅展示版启用
   斜向平铺「仅供效果展示」，铺满整页文档、不拦截任何操作
   用 absolute 而非 fixed：整页长截图的中段、末段才会同样带上水印
   关闭方式：删掉页面 <head> 里对 css/watermark.css 的引用
   ============================================================ */

body { position: relative; }

body::after {
    content: "";
    position: absolute;
    inset: 0;
    min-height: 100vh;
    z-index: 9999;
    pointer-events: none;
    user-select: none;
    background-image: url("../images/watermark-tile.png");
    background-repeat: repeat;
    background-size: 300px 190px;
    background-position: 0 0;
    opacity: .13;
    /* 白字 + 差值混合：白底呈浅灰、深色 banner 与照片上呈浅白，两种底都看得见 */
    mix-blend-mode: difference;
}

/* 老浏览器不支持混合模式时，把白字反相成深灰字 */
@supports not (mix-blend-mode: difference) {
    body::after {
        filter: invert(1);
        opacity: .09;
    }
}

@media (max-width: 860px) {
    body::after {
        background-size: 240px 152px;
        opacity: .12;
    }
}

@media (max-width: 520px) {
    body::after {
        background-size: 210px 133px;
        opacity: .11;
    }
}