/* 课件播放器 · 横屏 16:9 舞台 */
:root{
  --bg:#fdf8ec; --panel:#ffffff; --line:#ece0c6;
  --fg:#2b2740; --dim:#7b7367;
  --warm:#f08c1e; --cyan:#0f8fb8; --red:#e0483f; --green:#2f9e5f;
  --font:"PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;
  --math:"Times New Roman",Times,serif;
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{width:100%;height:100%;overflow:hidden;background:#efe6d2}
body{font-family:var(--font);color:var(--fg);-webkit-font-smoothing:antialiased}

/* ---------- 舞台：固定 1600×900，整体等比缩放到窗口 ---------- */
#stage{
  position:absolute;width:1600px;height:900px;
  transform-origin:0 0;
  background:var(--bg);
  /* 极淡的点阵，像稿纸：投影上几乎看不见，近看有质感 */
  background-image:radial-gradient(rgba(188,174,143,.30) 1px,transparent 1px);
  background-size:36px 36px;
  overflow:hidden;
}

/* ---------- 幻灯片 ---------- */
.slide{
  position:absolute;inset:0;padding:76px 92px 92px;
  display:flex;gap:56px;
  opacity:0;visibility:hidden;pointer-events:none;
  transition:opacity .28s ease,transform .28s ease;
  transform:translateX(28px);
}
.slide.cur{opacity:1;visibility:visible;pointer-events:auto;transform:none}

/* 左演示 / 右板书 */
.col{display:flex;flex-direction:column;justify-content:center;min-width:0}
.col.main{flex:1.42;gap:26px}
.col.side{flex:1;gap:26px}

/* 页眉：章节标签 */
.tag{
  position:absolute;left:92px;top:38px;
  font-size:20px;letter-spacing:.14em;color:var(--dim);
}
.tag b{color:var(--warm);font-weight:600}

/* 标题 */
h1{font-size:74px;line-height:1.22;font-weight:800;letter-spacing:-.01em}
h2{font-size:52px;line-height:1.3;font-weight:700}
/* 左栏标题下一道马克笔痕迹，不占高度（绝对定位），整套课件的统一笔迹 */
.col.main > h2{position:relative;isolation:isolate}
.col.main > h2::before{
  content:'';position:absolute;left:-8px;right:-8px;bottom:.08em;height:.30em;
  background:linear-gradient(90deg,rgba(240,140,30,.22),rgba(240,140,30,.07) 62%,rgba(240,140,30,0));
  border-radius:5px;z-index:-1;
}
h3{font-size:38px;line-height:1.4;font-weight:600;color:var(--fg)}
.sub{font-size:30px;color:var(--dim);line-height:1.6}
p,li{font-size:36px;line-height:1.72;color:var(--fg)}
ul{padding-left:1.15em;display:flex;flex-direction:column;gap:16px}
li::marker{color:var(--warm)}

/* 强调 */
.hl{color:var(--warm)}
.cy{color:var(--cyan)}
.rd{color:var(--red)}
.gr{color:var(--green)}
b,strong{font-weight:700;color:var(--warm)}

/* 卡片块 */
.card{
  background:var(--panel);border:1px solid var(--line);
  border-radius:18px;padding:30px 34px;
  box-shadow:0 2px 10px rgba(140,115,70,.07);
}
.card.tight{padding:22px 26px}

/* 公式（不引第三方库，用 HTML 排） */
.m{font-family:var(--math);font-size:46px;line-height:1.5;letter-spacing:.01em}
.m i{font-style:italic}
.m .sup{font-size:.62em;vertical-align:.52em;line-height:0}
.m .sub{font-size:.62em;vertical-align:-.25em;line-height:0;color:inherit}
.m-formula{display:block;text-align:center;padding:8px 0}

/* 画布容器：元件自己按容器尺寸绘制 */
.stage-box{
  flex:1;min-height:0;
  background:var(--panel);border:1px solid var(--line);
  border-radius:20px;overflow:hidden;position:relative;
  box-shadow:0 2px 14px rgba(140,115,70,.08);
}
.stage-box canvas{display:block;width:100%;height:100%}

/* 分步出现 */
/* 真分式：上分子、分数线、下分母 */
.fr{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;
  margin:0 .16em;font-size:.8em;line-height:1.06;position:relative;top:-.04em}
.fr>span:first-child{border-bottom:1.6px solid currentColor;padding:0 .22em .06em}
.fr>span:last-child{padding:.06em .22em 0}
/* 根式：√ 后面的被开方数挑一条上划线 */
.rad{white-space:nowrap}
.rad>i{font-style:normal;position:relative;padding:0 .1em 0 .02em}
.rad>i::after{content:'';position:absolute;left:0;right:.06em;top:.24em;height:1.6px;background:currentColor}
.frag{opacity:0;transform:translateY(14px);transition:opacity .3s,transform .3s}
.frag.on{opacity:1;transform:none}

/* 封面 */
.slide.cover{flex-direction:column;justify-content:center;gap:26px;padding-left:132px}
.slide.cover .kicker{font-size:26px;letter-spacing:.3em;color:var(--warm)}
.slide.cover h1{font-size:92px}
.slide.cover .rule{width:120px;height:5px;background:var(--warm);border-radius:3px;margin:12px 0 6px}

/* 收尾页 */
.slide.end{justify-content:center;align-items:center;text-align:center;flex-direction:column;gap:34px}

/* ---------- 书写层 ---------- */
#ink{
  /* width/height 必须写死 100%：canvas 有 width 属性（设备像素），不写就按位图尺寸撑开，
     在 Retina 上墨迹会整体偏移 */
  position:absolute;inset:0;width:100%;height:100%;z-index:10;touch-action:none;
  /* 笔形光标，热点在笔尖 (3,25)；不支持 SVG 光标的浏览器退回十字 */
  cursor:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='28' height='28' viewBox='0 0 28 28'%3E%3Cpath d='M3 25 4.8 18.4 18.6 4.6l4.8 4.8L9.6 23.2Z' fill='%23fff' stroke='%232b2740' stroke-width='1.5' stroke-linejoin='round'/%3E%3Cpath d='M3 25 4.8 18.4 9.6 23.2Z' fill='%23f08c1e'/%3E%3C/svg%3E") 3 25, crosshair;
}
#ink.off{pointer-events:none}
#ink.erasing{cursor:none}
#erRing{
  position:absolute;width:34px;height:34px;margin:-17px 0 0 -17px;border-radius:50%;
  border:1.5px solid rgba(43,39,64,.45);background:rgba(240,140,30,.10);
  pointer-events:none;z-index:11;display:none;
}
#erRing.on{display:block}

/* ---------- 编辑模式的选择框（照 PowerPoint：单击选中，八个手柄） ---------- */
#edSel{
  position:absolute;z-index:50;display:none;pointer-events:none;
  border:1.5px solid var(--warm);border-radius:3px;
}
#edSel.on{display:block}
.ed-handle{
  position:absolute;width:12px;height:12px;margin:-6px 0 0 -6px;
  background:#fff;border:1.5px solid var(--warm);border-radius:3px;
  box-shadow:0 1px 4px rgba(140,115,70,.25);pointer-events:auto;
}
.ed-handle[data-h="nw"]{left:0;top:0;cursor:nwse-resize}
.ed-handle[data-h="n"]{left:50%;top:0;cursor:ns-resize}
.ed-handle[data-h="ne"]{left:100%;top:0;cursor:nesw-resize}
.ed-handle[data-h="e"]{left:100%;top:50%;cursor:ew-resize}
.ed-handle[data-h="se"]{left:100%;top:100%;cursor:nwse-resize}
.ed-handle[data-h="s"]{left:50%;top:100%;cursor:ns-resize}
.ed-handle[data-h="sw"]{left:0;top:100%;cursor:nesw-resize}
.ed-handle[data-h="w"]{left:0;top:50%;cursor:ew-resize}

/* 能按住拖的东西给个 move 光标，白底块悬停描一圈虚线 */
.editing .slide{cursor:default}
.editing .slide .card,.editing .slide .stage-box,.editing .slide .txt-box{cursor:move}
.editing .slide .card:hover,.editing .slide .stage-box:hover,.editing .slide .txt-box:hover{
  outline:1px dashed rgba(240,140,30,.45);outline-offset:4px;
}
.editing .slide [contenteditable]{cursor:text}

/* 编辑模式里加的独立文字块：白底盖得住画布上原有的字 */
.txt-box{
  position:absolute;z-index:8;min-width:60px;min-height:46px;padding:2px 10px;
  font-family:var(--font);font-size:34px;line-height:1.4;color:var(--fg);
  background:rgba(255,255,255,.94);border-radius:6px;
}

/* ---------- 小弹窗：轻点带 data-pop 的文字浮出来 ---------- */
[data-pop]{cursor:pointer}
[data-pop]::after{
  content:'▶';font-size:.4em;vertical-align:.8em;margin-left:.45em;
  color:var(--warm);opacity:.5;letter-spacing:0;
}
[data-pop]:hover::after{opacity:1}

#popMask{
  position:absolute;inset:0;z-index:40;display:none;
  background:rgba(43,39,64,.34);backdrop-filter:blur(3px);
}
#popMask.on{display:block}
.pop-box{
  position:absolute;left:50%;top:50%;transform:translate(-50%,-50%) scale(.94);
  width:1040px;height:660px;background:var(--panel);
  border:1px solid var(--line);border-radius:24px;overflow:hidden;
  box-shadow:0 26px 64px rgba(60,45,20,.30);
  transition:transform .22s ease;
}
#popMask.on .pop-box{transform:translate(-50%,-50%) scale(1)}
.pop-box canvas{display:block;width:100%;height:100%}
.pop-x{
  position:absolute;right:16px;top:14px;
  width:34px;height:34px;border-radius:50%;display:grid;place-items:center;
  background:rgba(253,248,236,.9);border:1px solid var(--line);
  color:var(--dim);font-size:15px;font-style:normal;
}

/* ---------- 底部 HUD ---------- */
#hud{
  position:absolute;left:0;right:0;bottom:0;height:64px;
  display:flex;align-items:center;gap:18px;padding:0 34px;
  font-size:19px;color:var(--dim);z-index:20;
  background:linear-gradient(to top,rgba(253,248,236,.92),rgba(253,248,236,0));
  pointer-events:none;
}
#bar{flex:1;height:3px;background:var(--line);border-radius:2px;overflow:hidden;margin:0 8px}
#bar i{display:block;height:100%;width:0;background:var(--warm);transition:width .28s ease}
#idx{font-family:var(--math);font-size:21px;color:var(--fg);min-width:76px;text-align:right}

/* ---------- 工具栏 ---------- */
#tools{
  position:absolute;left:34px;bottom:78px;z-index:30;
  display:flex;align-items:center;gap:8px;
  padding:9px 12px;border-radius:999px;
  background:rgba(255,255,255,.94);border:1px solid var(--line);
  backdrop-filter:blur(8px);box-shadow:0 2px 10px rgba(140,115,70,.10);
  transition:opacity .25s;
}
#tools.hide{opacity:0;pointer-events:none}
#tools button{
  width:38px;height:38px;border-radius:50%;border:1px solid transparent;
  background:transparent;color:var(--dim);cursor:pointer;font-size:17px;
  display:grid;place-items:center;font-family:var(--font);
  transition:.18s;
}
#tools button:hover{color:var(--fg);background:rgba(0,0,0,.05)}
#tools button.act{color:#fff;background:var(--warm);border-color:var(--warm)}
#tools .sep{width:1px;height:22px;background:var(--line);margin:0 4px}
#tools .dot{width:26px;height:26px;border-radius:50%;border:2px solid transparent;cursor:pointer}
#tools .dot.act{border-color:var(--fg);transform:scale(1.08)}

/* 全屏提示 */
#hint{
  position:absolute;left:50%;bottom:96px;transform:translateX(-50%);z-index:25;
  font-size:17px;color:var(--dim);background:rgba(255,255,255,.94);
  border:1px solid var(--line);border-radius:999px;padding:9px 20px;
  transition:opacity .5s;
}
#hint.hide{opacity:0}