:root{
  --bg:#f9f9f9; --card:#ffffff; --text:#0f0f0f; --text-2:#606060;
  --line:#e5e5e5; --accent:#e5484d; --accent-dark:#c93a3f;
  --chip:#f2f2f2; --chip-on:#0f0f0f; --link:#065fd4;
  --radius:12px; --shadow:0 1px 2px rgba(0,0,0,.08);
}
@media (prefers-color-scheme: dark){
  :root{
    --bg:#0f0f0f; --card:#1c1c1e; --text:#f1f1f1; --text-2:#aaaaaa;
    --line:#303030; --chip:#272727; --chip-on:#f1f1f1; --link:#3ea6ff;
    --shadow:0 1px 2px rgba(0,0,0,.4);
  }
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth;scroll-padding-top:64px}
body{
  font-family:"PingFang SC","Microsoft YaHei","Helvetica Neue",Arial,sans-serif;
  background:var(--bg); color:var(--text); line-height:1.75;
  -webkit-font-smoothing:antialiased;
}
a{color:var(--link);text-decoration:none}
a:hover{text-decoration:underline}

/* ===== 顶栏 ===== */
.topbar{
  position:fixed;top:0;left:0;right:0;z-index:50;height:56px;
  display:flex;align-items:center;gap:16px;padding:0 16px;
  background:var(--card);border-bottom:1px solid var(--line);
}
.brand{display:flex;align-items:center;gap:8px;font-size:18px;font-weight:700;color:var(--text)}
.brand:hover{text-decoration:none}
.brand-logo{width:26px;height:26px;flex:none}
.brand small{font-size:12px;font-weight:400;color:var(--text-2)}
.topnav{margin-left:auto;display:flex;gap:2px}
.topnav a{
  color:var(--text-2);font-size:14px;padding:6px 10px;border-radius:8px;white-space:nowrap;
}
.topnav a:hover{background:var(--chip);color:var(--text);text-decoration:none}
.menu-btn{
  display:none;margin-left:auto;width:40px;height:40px;border:none;border-radius:50%;
  background:transparent;cursor:pointer;align-items:center;justify-content:center;
  -webkit-tap-highlight-color:transparent;
}
.menu-btn:hover{background:var(--chip)}
.menu-btn span{
  position:relative;display:block;width:18px;height:2px;background:var(--text);
  border-radius:1px;transition:background .2s;
}
.menu-btn span::before,.menu-btn span::after{
  content:"";position:absolute;left:0;width:18px;height:2px;background:var(--text);
  border-radius:1px;transition:transform .2s,top .2s;
}
.menu-btn span::before{top:-6px}
.menu-btn span::after{top:6px}
.topbar.open .menu-btn span{background:transparent}
.topbar.open .menu-btn span::before{top:0;transform:rotate(45deg)}
.topbar.open .menu-btn span::after{top:0;transform:rotate(-45deg)}

@media (max-width:760px){
  .menu-btn{display:inline-flex}
  .topnav{
    display:none;position:absolute;top:56px;left:0;right:0;
    flex-direction:column;gap:0;padding:6px 0;
    background:var(--card);border-bottom:1px solid var(--line);
    box-shadow:0 8px 20px rgba(0,0,0,.12);
  }
  .topbar.open .topnav{display:flex}
  .topnav a{padding:12px 20px;border-radius:0;font-size:15px;color:var(--text)}
}

.wrap{max-width:960px;margin:0 auto;padding:72px 16px 40px}
.card{
  background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  box-shadow:var(--shadow);padding:24px;margin-bottom:20px;
}
section h2{font-size:20px;margin-bottom:14px;display:flex;align-items:center;gap:8px}
section h2::before{content:"";width:4px;height:18px;border-radius:2px;background:var(--accent);flex:none}
section h3{font-size:16px;margin:16px 0 6px}
section p{color:var(--text-2);margin-bottom:10px}
section p strong,section li strong{color:var(--text)}
section ul,section ol{padding-left:22px;color:var(--text-2)}
section li{margin-bottom:6px}

/* ===== 工具区 ===== */
.hero h1{font-size:24px;margin-bottom:6px}
.hero .sub{color:var(--text-2);font-size:14px;margin-bottom:16px}
.badges{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:16px}
.badges span{
  font-size:12px;padding:3px 10px;border-radius:99px;
  background:var(--chip);color:var(--text-2);
}
.image-area{
  position:relative;min-height:240px;border-radius:var(--radius);
  border:2px dashed var(--line);background:var(--bg);
  display:flex;align-items:center;justify-content:center;
  text-align:center;overflow:hidden;transition:border-color .2s,background .2s;
}
.image-area.dragover{border-color:var(--accent);background:rgba(229,72,77,.06)}
.image-area img{max-width:100%;max-height:70vh;display:none;border-radius:8px}
.drop-hint{color:var(--text-2);font-size:14px;padding:24px;pointer-events:none}
.drop-hint b{display:block;font-size:16px;color:var(--text);margin-bottom:4px}
.processing-overlay{
  position:absolute;inset:0;display:flex;align-items:center;justify-content:center;
  background:rgba(0,0,0,.35);border-radius:var(--radius);
}
.processing-overlay[hidden]{display:none}
.processing-toast{
  display:flex;align-items:center;gap:10px;background:var(--card);color:var(--text);
  padding:10px 18px;border-radius:99px;box-shadow:0 4px 16px rgba(0,0,0,.25);font-size:14px;
}
.processing-spinner{
  width:16px;height:16px;border-radius:50%;flex:none;
  border:2px solid var(--line);border-top-color:var(--accent);
  animation:spin .8s linear infinite;
}
@keyframes spin{to{transform:rotate(360deg)}}
.file-meta{font-size:13px;color:var(--text-2);margin-top:10px;min-height:20px;word-break:break-all}
.controls{margin-top:14px}
.controls-row{display:flex;flex-wrap:wrap;gap:10px}
.normal_button{
  position:relative;display:inline-flex;align-items:center;justify-content:center;gap:6px;
  min-height:40px;padding:0 20px;border:none;border-radius:99px;cursor:pointer;
  font-size:14px;font-weight:500;font-family:inherit;
  background:var(--chip);color:var(--text);transition:filter .15s,transform .05s;
  -webkit-tap-highlight-color:transparent;user-select:none;
}
.normal_button:hover{filter:brightness(.94)}
.normal_button:active{transform:scale(.97)}
.normal_button:disabled{opacity:.45;cursor:not-allowed;transform:none}
.upload_button{background:var(--accent);color:#fff}
.upload_button:hover{background:var(--accent-dark);filter:none}
.ipt_btn{position:absolute;inset:0;opacity:0;cursor:pointer;font-size:0}
#download{background:var(--chip-on);color:var(--card)}
.toast{
  position:fixed;left:50%;bottom:32px;transform:translateX(-50%) translateY(10px);
  background:var(--chip-on);color:var(--card);font-size:14px;
  padding:10px 20px;border-radius:99px;opacity:0;pointer-events:none;
  transition:opacity .25s,transform .25s;z-index:99;max-width:86vw;
}
.toast.show{opacity:1;transform:translateX(-50%) translateY(0)}

/* ===== 步骤 / 场景卡片 ===== */
.grid{display:grid;gap:14px;grid-template-columns:repeat(auto-fit,minmax(210px,1fr))}
.mini{
  background:var(--bg);border:1px solid var(--line);border-radius:var(--radius);padding:16px;
}
.mini .num{
  display:inline-flex;align-items:center;justify-content:center;
  width:26px;height:26px;border-radius:50%;background:var(--accent);color:#fff;
  font-size:13px;font-weight:700;margin-bottom:8px;
}
.mini h3{margin:0 0 4px;font-size:15px}
.mini p{font-size:13px;margin:0}

/* ===== 原理示意 ===== */
.demo-row{display:flex;flex-wrap:wrap;gap:16px;align-items:center;justify-content:center;margin:14px 0}
.demo-cell{text-align:center}
.demo-cell canvas{
  width:150px;height:150px;border-radius:8px;border:1px solid var(--line);
  image-rendering:pixelated;display:block;background:var(--bg);
}
.demo-cell span{font-size:12px;color:var(--text-2)}
.demo-arrow{font-size:20px;color:var(--text-2)}
.formula{
  background:var(--bg);border:1px solid var(--line);border-radius:8px;
  padding:12px 16px;font-family:ui-monospace,Menlo,Consolas,monospace;
  font-size:13px;color:var(--text);overflow-x:auto;margin:10px 0;
}

/* ===== 对比表 ===== */
table{width:100%;border-collapse:collapse;font-size:14px;margin:10px 0}
th,td{border:1px solid var(--line);padding:9px 12px;text-align:left;color:var(--text-2)}
th{background:var(--bg);color:var(--text);font-weight:600;white-space:nowrap}

/* ===== FAQ ===== */
details{border-bottom:1px solid var(--line);padding:4px 0}
details:last-of-type{border-bottom:none}
summary{
  cursor:pointer;font-weight:600;padding:10px 0;list-style:none;
  display:flex;justify-content:space-between;align-items:center;gap:12px;
}
summary::-webkit-details-marker{display:none}
summary::after{content:"+";font-size:18px;color:var(--text-2);flex:none;transition:transform .2s}
details[open] summary::after{transform:rotate(45deg)}
details p{padding-bottom:12px}

/* ===== 更新日志 ===== */
.log{list-style:none;padding:0}
.log li{
  position:relative;padding:0 0 14px 22px;margin:0;border-left:2px solid var(--line);
  margin-left:6px;
}
.log li::before{
  content:"";position:absolute;left:-6px;top:6px;width:10px;height:10px;
  border-radius:50%;background:var(--accent);
}
.log time{font-size:12px;color:var(--text-2);display:block}

/* ===== 页脚 ===== */
footer{
  border-top:1px solid var(--line);background:var(--card);
  padding:28px 16px calc(28px + env(safe-area-inset-bottom));text-align:center;
}
footer p{font-size:13px;color:var(--text-2);margin-bottom:6px}
footer nav{display:flex;gap:16px;justify-content:center;flex-wrap:wrap;margin-bottom:10px}
footer nav a{font-size:13px;color:var(--text-2)}

@media (max-width:600px){
  .card{padding:18px 16px}
  .hero h1{font-size:21px}
  .controls-row{display:grid;grid-template-columns:1fr 1fr}
  .normal_button{width:100%}
  .image-area img{max-height:47vh}
}
/* ===== 广告位(默认不占位,注入广告时撑开) ===== */
.ad-wrap{display:none;justify-content:center;margin:0 0 5px}
.ad-wrap.on{display:flex}
.ad-wrap.on + .file-meta{margin-top:0}
.ad-slot{width:320px;height:50px;overflow:hidden}