:root{
  --bg:#faf9f7; --fg:#1c1a17; --muted:#6b655c; --line:#e3ded5;
  --accent:#1f6f5c; --accent-2:#17594a; --card:#fff; --warn:#a8442a;
  --radius:12px; --maxw:900px;
}
@media (prefers-color-scheme:dark){
  :root{ --bg:#14140f; --fg:#f2efe8; --muted:#a49c8f; --line:#2c2a22; --card:#1d1c16; --accent:#5fd0ab; --accent-2:#7fe0c0; }
}
*{box-sizing:border-box}
html,body{margin:0;padding:0}
body{
  background:var(--bg); color:var(--fg);
  font:16px/1.6 ui-sans-serif,system-ui,-apple-system,"Segoe UI","Noto Sans SC",sans-serif;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--accent)}
.topbar{
  display:flex; align-items:center; gap:16px; flex-wrap:wrap;
  max-width:var(--maxw); margin:0 auto; padding:14px 20px;
  border-bottom:1px solid var(--line);
}
.brand{font-weight:700; text-decoration:none; color:var(--fg)}
.family{display:flex; gap:8px; margin-left:auto; flex-wrap:wrap}
.family a{
  text-decoration:none; color:var(--muted); font-size:14px;
  padding:4px 10px; border:1px solid var(--line); border-radius:999px;
}
.family a[aria-current="page"]{color:var(--fg); border-color:var(--accent)}
.langs{display:flex; gap:6px; font-size:13px}
.langs a{text-decoration:none; color:var(--muted)}
.langs a[aria-current="true"]{color:var(--fg); font-weight:600}

.page{max-width:var(--maxw); margin:0 auto; padding:32px 20px 64px}
.hero-title{font-size:clamp(24px,4vw,36px); line-height:1.25; margin:0 0 12px}
.hero-text{color:var(--muted); max-width:62ch; margin:0 0 28px}

.tool{background:var(--card); border:1px solid var(--line); border-radius:var(--radius); padding:20px}
.drop{
  border:2px dashed var(--line); border-radius:var(--radius);
  padding:36px 20px; text-align:center; transition:border-color .15s, background .15s;
}
.drop.is-over{border-color:var(--accent); background:color-mix(in srgb, var(--accent) 6%, transparent)}
.drop__text{margin:0 0 14px; color:var(--muted)}
.drop__note{margin:12px 0 0; font-size:13px; color:var(--muted)}

.btn{
  display:inline-flex; align-items:center; justify-content:center; gap:8px;
  font:inherit; padding:9px 16px; border-radius:9px; cursor:pointer;
  border:1px solid var(--line); background:transparent; color:var(--fg);
}
.btn:disabled{opacity:.45; cursor:not-allowed}
.btn--primary{background:var(--accent); border-color:var(--accent); color:#fff}
.btn--small{padding:5px 10px; font-size:14px}

.panel{margin-top:22px}
.controls{display:grid; gap:16px; padding-bottom:18px; border-bottom:1px solid var(--line)}
.control{display:flex; align-items:center; gap:12px; flex-wrap:wrap}
.control>span:first-child{min-width:64px; color:var(--muted)}
.control input[type=range]{flex:1; min-width:180px; accent-color:var(--accent)}
.control output{min-width:36px; text-align:right; font-variant-numeric:tabular-nums}
.control--check{align-items:flex-start}
.control--check small{display:block; color:var(--muted); font-size:13px}
.notice{
  margin:0 0 16px; padding:12px 14px; border-radius:10px;
  border:1px solid #b45309; background:rgba(180,83,9,.12); color:inherit; font-size:14px;
}
.file__hint{margin:2px 0 8px; color:var(--muted); font-size:12px}
.file__hint.is-warn{color:#b45309}
.file__exif{margin:-4px 0 8px; color:var(--muted); font-size:12px}
.file__exif.is-warn{color:#b45309; font-weight:600}
.file__exif:empty{display:none}
.drop.is-disabled{opacity:.5; pointer-events:none}

/* 只给读屏软件看的文字（用于 aria-live 状态播报） */
.sr-only{
  position:absolute; width:1px; height:1px; padding:0; margin:-1px;
  overflow:hidden; clip:rect(0 0 0 0); white-space:nowrap; border:0;
}
/* 键盘焦点必须可见 —— 否则键盘用户完全不知道焦点在哪 */
.file__slider:focus-visible{outline:2px solid currentColor; outline-offset:2px}
.btn:focus-visible, a:focus-visible, input:focus-visible{outline:2px solid currentColor; outline-offset:2px}

/* ---- 广告位：预留高度，避免广告加载时把内容顶下去（CLS 是 SEO 负项） ---- */
.ad{
  display:block; margin:22px 0; min-height:100px;
  background:transparent;
}
.ad:empty{display:none}
.ad ins{display:block}

/* ---- 内容页（How-to / 指南） ---- */
.post{max-width:70ch}
.post h2{margin:28px 0 10px; font-size:20px}
.post h3{margin:22px 0 8px; font-size:17px}
.post p{margin:0 0 14px; line-height:1.75}
.post ul{margin:0 0 14px; padding-left:22px}
.post li{margin:0 0 7px; line-height:1.7}
.post code{background:rgba(127,127,127,.16); padding:1px 5px; border-radius:5px; font-size:.92em}
.post__meta{color:var(--muted); font-size:13px; margin:0 0 18px}
.cta{margin:30px 0}
.guides{list-style:none; padding:0; max-width:70ch}
.guides li{margin:0 0 18px; padding-bottom:16px; border-bottom:1px solid var(--line)}
.guides small{color:var(--muted); line-height:1.6}
.related{margin-top:34px}
.related ul{padding-left:20px}
.related li{margin-bottom:8px}
.control--modes{gap:16px}
.control--modes .radio{display:inline-flex; align-items:center; gap:6px; cursor:pointer}
.control input[type=number]{
  width:96px; padding:7px 10px; font:inherit; color:var(--fg);
  background:transparent; border:1px solid var(--line); border-radius:8px;
}
.control .unit{color:var(--muted); font-size:14px}
.controls__actions{display:flex; gap:10px}

.files{list-style:none; margin:18px 0 0; padding:0; display:grid; gap:14px}
.file{border:1px solid var(--line); border-radius:var(--radius); padding:12px}
.file__head{display:flex; align-items:center; gap:8px; margin-bottom:10px}
.file__name{flex:1; font-size:14px; overflow:hidden; text-overflow:ellipsis; white-space:nowrap}
.file__remove{border:0; background:none; color:var(--muted); font-size:20px; line-height:1; cursor:pointer}
.file__compare{position:relative; overflow:hidden; border-radius:8px; background:#0002}
.file__img{display:block; width:100%; height:auto; max-height:320px; object-fit:contain}
.file__slider{position:absolute; inset:0; cursor:ew-resize}
.file__after{position:absolute; inset:0; background-size:contain; background-position:center; background-repeat:no-repeat; clip-path:inset(0 50% 0 0)}
.file__handle{position:absolute; top:0; bottom:0; left:50%; width:2px; background:#fff; box-shadow:0 0 0 1px #0006}
.file__meta{display:flex; align-items:center; gap:12px; margin-top:10px; font-size:14px; flex-wrap:wrap}
.file__state{color:var(--muted)}
.file__sizes{font-variant-numeric:tabular-nums}
.file__meta .btn--small{margin-left:auto; text-decoration:none}
.is-error .file__state{color:var(--warn)}

.about{margin-top:40px; color:var(--muted)}
.about h2{font-size:18px; color:var(--fg)}
.privacy{font-size:14px}
.footer{
  max-width:var(--maxw); margin:0 auto; padding:20px;
  border-top:1px solid var(--line); color:var(--muted); font-size:14px;
  display:flex; gap:16px; flex-wrap:wrap;
}