/* ==========================================================================
   Gemini 风格视觉：极光背景 + 玻璃拟态 + 渐变强调 + 入场动效
   排版只用一套固定阶梯（5 档字号 / 3 档字重），避免字号字重满天飞。
   ========================================================================== */

/* ===== 设计变量 ===== */
:root {
  /* 品牌色：Google 蓝 → 紫 → 珊瑚粉 */
  --brand-1: #4285f4;
  --brand-2: #9b72cb;
  --brand-3: #d96570;

  /* 字号阶梯：xs 标注 / sm 控件 / md 正文 / lg 小标题 / xl 章节标题 */
  --fs-xs: 12.5px;
  --fs-sm: 13.5px;
  --fs-md: 15px;
  --fs-lg: 17px;
  --fs-xl: 21px;
  --fs-hero: clamp(28px, 4.4vw, 44px);

  --bg: #08090d;
  --bg-elev: rgba(255, 255, 255, 0.045);
  --bg-elev-2: rgba(255, 255, 255, 0.075);
  --bg-inset: rgba(0, 0, 0, 0.26);
  --surface: rgba(255, 255, 255, 0.045);
  --border: rgba(255, 255, 255, 0.10);
  --border-strong: rgba(255, 255, 255, 0.20);

  --text: #eef1f6;
  --text-dim: #a4abb8;
  --text-faint: #737b89;

  --accent: var(--brand-1);
  --accent-soft: color-mix(in srgb, var(--brand-1) 16%, transparent);
  --accent-line: color-mix(in srgb, var(--brand-1) 55%, transparent);

  --ok: #3fb950;
  --warn: #e3b341;
  --err: #ff7b72;

  --radius: 20px;
  --radius-sm: 12px;
  --shadow: 0 30px 60px -40px rgba(0, 0, 0, 0.95);
  --aurora-opacity: 0.5;
  --page: 1180px;

  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: system-ui, -apple-system, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
}

html[data-theme="light"] {
  --bg: #f7f9fd;
  --bg-elev: rgba(255, 255, 255, 0.75);
  --bg-elev-2: rgba(15, 23, 42, 0.045);
  --bg-inset: rgba(255, 255, 255, 0.9);
  --surface: rgba(255, 255, 255, 0.72);
  --border: rgba(15, 23, 42, 0.10);
  --border-strong: rgba(15, 23, 42, 0.20);

  --text: #14171c;
  --text-dim: #55606f;
  --text-faint: #818b99;

  --accent: #1a73e8;
  --accent-soft: rgba(26, 115, 232, 0.10);
  --accent-line: rgba(26, 115, 232, 0.40);

  --ok: #1a7f37;
  --warn: #9a6700;
  --err: #d1242f;

  --shadow: 0 26px 50px -34px rgba(23, 43, 77, 0.35);
  --aurora-opacity: 0.3;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: var(--fs-md);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

::selection { background: color-mix(in srgb, var(--brand-2) 35%, transparent); }

/* ===== 会缓慢流动的极光背景 ===== */
body::before {
  content: "";
  position: fixed;
  inset: -25vmax;
  z-index: -2;
  pointer-events: none;
  opacity: var(--aurora-opacity);
  background:
    radial-gradient(40vmax 40vmax at 18% 10%, var(--brand-1), transparent 62%),
    radial-gradient(36vmax 36vmax at 84% 6%, var(--brand-2), transparent 62%),
    radial-gradient(44vmax 44vmax at 62% 92%, var(--brand-3), transparent 66%);
  filter: blur(72px) saturate(135%);
  animation: aurora 28s ease-in-out infinite alternate;
}

body::after {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background: radial-gradient(120% 90% at 50% 0%, transparent 30%, color-mix(in srgb, var(--bg) 78%, transparent) 100%);
}

@keyframes aurora {
  0%   { transform: translate3d(-2%, -1%, 0) scale(1)    rotate(0deg); }
  50%  { transform: translate3d(3%, 2%, 0)   scale(1.07) rotate(4deg); }
  100% { transform: translate3d(-1%, 3%, 0)  scale(1.03) rotate(-3deg); }
}

/* ===== 顶栏 ===== */
.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 10px clamp(16px, 3vw, 28px);
  border-bottom: 1px solid var(--border);
  background: color-mix(in srgb, var(--bg) 68%, transparent);
  backdrop-filter: blur(20px) saturate(180%);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--text);
  text-decoration: none;
  font-size: var(--fs-md);
  font-weight: 600;
  flex: none;
}

.brand-mark {
  width: 32px; height: 32px;
  display: grid; place-items: center;
  border-radius: 11px;
  color: #fff;
  background: linear-gradient(140deg, var(--brand-1), var(--brand-2) 60%, var(--brand-3));
  background-size: 180% auto;
  box-shadow: 0 8px 20px -10px var(--brand-2);
  transition: transform .4s cubic-bezier(.2,.8,.3,1), background-position .6s ease;
}
.brand:hover .brand-mark { transform: rotate(-8deg) scale(1.06); background-position: 100% center; }

.brand-text { font-size: var(--fs-md); font-weight: 600; letter-spacing: 0.01em; }

.topbar-actions { display: flex; align-items: center; gap: 6px; flex: none; margin-left: auto; }

.ghost-link {
  color: var(--text-dim);
  text-decoration: none;
  font-size: var(--fs-sm);
  padding: 6px 12px;
  border-radius: 999px;
  transition: color .2s, background .2s;
}
.ghost-link:hover { color: var(--text); background: var(--bg-elev-2); }

.icon-btn {
  display: grid; place-items: center;
  width: 36px; height: 36px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-elev);
  color: var(--text-dim);
  cursor: pointer;
  transition: transform .35s cubic-bezier(.2,.8,.3,1), color .2s, border-color .2s, box-shadow .3s;
}
.icon-btn:hover {
  color: var(--text);
  border-color: var(--border-strong);
  transform: rotate(18deg) scale(1.06);
  box-shadow: 0 0 0 6px color-mix(in srgb, var(--brand-1) 12%, transparent);
}
html[data-theme="dark"] .i-sun { display: none; }
html[data-theme="light"] .i-moon { display: none; }

/* ===== 主体：整页铺开，桌面双栏 ===== */
.app {
  flex: 1;
  width: 100%;
  max-width: var(--page);
  margin: 0 auto;
  padding: 22px clamp(16px, 3vw, 28px) 60px;
}

/* ===== 首屏 ===== */
.hero {
  position: relative;
  text-align: center;
  padding: 22px 0 24px;
}

.hero::before {
  content: "";
  position: absolute;
  left: 50%; top: -80px;
  width: 520px; height: 320px;
  transform: translateX(-50%);
  background: radial-gradient(closest-side, color-mix(in srgb, var(--brand-2) 32%, transparent), transparent 70%);
  filter: blur(50px);
  pointer-events: none;
  z-index: -1;
  animation: breathe 9s ease-in-out infinite;
}

@keyframes breathe {
  0%, 100% { opacity: .5; transform: translateX(-50%) scale(1); }
  50%      { opacity: .9; transform: translateX(-50%) scale(1.12); }
}

.hero h1 {
  margin: 0 0 12px;
  font-size: var(--fs-hero);
  line-height: 1.16;
  font-weight: 600;
  letter-spacing: -0.03em;
  background: linear-gradient(100deg,
    var(--text) 6%, var(--brand-1) 30%, var(--brand-2) 48%, var(--brand-3) 64%, var(--text) 94%);
  background-size: 260% auto;
  -webkit-background-clip: text;
  background-clip: text;
  color: transparent;
  -webkit-text-fill-color: transparent;
  animation: sheen 10s linear infinite;
}

@keyframes sheen { to { background-position: 260% center; } }

.hero p {
  margin: 0 auto;
  max-width: 60ch;
  color: var(--text-dim);
}
.hero p strong { color: var(--text); font-weight: 500; }

.hero-note {
  margin-top: 12px !important;
  font-size: var(--fs-sm) !important;
  color: var(--text-faint) !important;
}

.hero-badges {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
  margin-top: 16px;
}
.badge {
  display: inline-flex;
  align-items: center;
  gap: 7px;
  font-size: var(--fs-xs);
  color: var(--text-dim);
  padding: 5px 13px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  backdrop-filter: blur(10px);
  transition: transform .25s cubic-bezier(.2,.8,.3,1), color .2s, border-color .2s;
}
.badge:hover { transform: translateY(-2px); color: var(--text); border-color: var(--border-strong); }
.badge .dot {
  width: 6px; height: 6px; border-radius: 50%;
  background: linear-gradient(140deg, var(--brand-1), var(--brand-2));
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--brand-1) 16%, transparent);
}

/* ===== 工具区：左主右辅 ===== */
.tool-grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 336px;
  gap: 18px;
  align-items: start;
}
.tool-main { grid-column: 1; grid-row: 1; min-width: 0; }
.tool-side { grid-column: 2; grid-row: 1; min-width: 0; display: grid; gap: 14px; }

@media (min-width: 981px) {
  .tool-side { position: sticky; top: 76px; }
}

@media (max-width: 980px) {
  .tool-grid { grid-template-columns: minmax(0, 1fr); }
  .tool-main, .tool-side { grid-column: 1; grid-row: auto; }
}

/* 工具导航：注册表里有 2 个以上工具时由 app.js 渲染出来 */
.tool-rail {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 14px;
}
.tool-chip {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 7px 15px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--surface);
  backdrop-filter: blur(10px);
  color: var(--text-dim);
  text-decoration: none;
  font-size: var(--fs-sm);
  transition: transform .2s cubic-bezier(.2,.8,.3,1), color .2s, border-color .2s, box-shadow .3s;
}
.tool-chip:hover { transform: translateY(-2px); color: var(--text); border-color: var(--border-strong); }
.tool-chip.active {
  color: #fff;
  border-color: transparent;
  background: linear-gradient(100deg, var(--brand-1), var(--brand-2));
  box-shadow: 0 10px 24px -14px var(--brand-2);
}
.tool-chip .glyph {
  font-family: var(--mono);
  font-size: var(--fs-xs);
  opacity: .85;
}

/* ===== 玻璃面板 ===== */
.panel {
  position: relative;
  padding: 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  background: linear-gradient(180deg, var(--surface), color-mix(in srgb, var(--surface) 35%, transparent));
  backdrop-filter: blur(16px);
  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.06) inset, var(--shadow);
  transition: border-color .3s, box-shadow .35s;
}
.panel + .panel { margin-top: 14px; }
.panel:focus-within {
  border-color: color-mix(in srgb, var(--brand-1) 45%, var(--border));
  box-shadow: 0 1px 0 rgba(255, 255, 255, 0.06) inset,
              0 0 0 4px color-mix(in srgb, var(--brand-1) 12%, transparent),
              0 34px 70px -44px color-mix(in srgb, var(--brand-1) 70%, transparent);
}

/* ===== 步骤小标题（工具区 / 侧栏共用） ===== */
.prompt-head { display: flex; align-items: center; gap: 10px; margin: 0 0 10px; }
.prompt-title {
  margin: 0;
  font-size: var(--fs-lg);
  font-weight: 600;
  letter-spacing: -0.01em;
}
.step {
  flex: none;
  font-size: var(--fs-xs);
  font-weight: 500;
  padding: 3px 10px;
  border-radius: 999px;
  color: #fff;
  background: linear-gradient(100deg, var(--brand-1), var(--brand-2));
  box-shadow: 0 6px 16px -10px var(--brand-2);
}

/* ===== 提示词卡片 ===== */
.prompt-card { overflow: hidden; }
.prompt-card::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 2px;
  background: linear-gradient(90deg, var(--brand-1), var(--brand-2), var(--brand-3), var(--brand-1));
  background-size: 220% auto;
  animation: sheen 6s linear infinite;
}

.prompt-lead { margin: 0 0 12px; font-size: var(--fs-sm); color: var(--text-dim); }
.prompt-lead strong { color: var(--text); font-weight: 500; }

.prompt-box {
  position: relative;
  margin: 0 0 12px;
  padding: 12px 14px 12px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-inset);
  font-size: var(--fs-sm);
  line-height: 1.7;
  white-space: pre-wrap;
  word-break: break-word;
}
.prompt-box::before {
  content: "";
  position: absolute;
  left: 0; top: 12px; bottom: 12px;
  width: 3px;
  border-radius: 0 3px 3px 0;
  background: linear-gradient(180deg, var(--brand-1), var(--brand-2), var(--brand-3));
}
.prompt-box::after {
  content: "▍";
  margin-left: 2px;
  color: var(--brand-2);
  animation: blink 1.15s steps(2, start) infinite;
}

@keyframes blink { 50% { opacity: 0; } }

/* ===== 侧栏小卡片 ===== */
.side-title { margin: 0 0 10px; font-size: var(--fs-md); font-weight: 600; }
.link-list { margin: 0; padding: 0; list-style: none; display: grid; gap: 2px; }
.link-list a {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 8px 10px;
  border-radius: 10px;
  color: var(--text-dim);
  text-decoration: none;
  font-size: var(--fs-sm);
  transition: background .2s, color .2s, transform .2s;
}
.link-list a:hover { background: var(--bg-elev-2); color: var(--text); transform: translateX(3px); }
.link-list a::after { content: "→"; color: var(--text-faint); transition: transform .2s; }
.link-list a:hover::after { transform: translateX(3px); color: var(--accent); }

/* ===== 表单控件 ===== */
.field { display: block; }

.lbl {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 8px;
  margin-bottom: 8px;
  font-size: var(--fs-sm);
  font-weight: 500;
  color: var(--text-dim);
}
.hint { margin: 0; font-weight: 400; font-size: var(--fs-xs); color: var(--text-faint); }

textarea, input[type="text"], input[type="number"], select, input[type="file"] {
  padding: 11px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: color-mix(in srgb, var(--bg-inset) 80%, transparent);
  color: var(--text);
  font-family: inherit;
  font-size: var(--fs-sm);
  outline: none;
  transition: border-color .2s, box-shadow .3s, background .2s;
}
textarea, input[type="text"], input[type="number"] { width: 100%; }

textarea {
  font-family: var(--mono);
  line-height: 1.75;
  resize: vertical;
  tab-size: 2;
}
textarea::placeholder, input::placeholder { color: var(--text-faint); }

textarea:focus, input:focus, select:focus {
  border-color: color-mix(in srgb, var(--brand-1) 55%, transparent);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--brand-1) 15%, transparent);
  background: color-mix(in srgb, var(--bg-inset) 60%, transparent);
}

select { width: auto; min-width: 92px; max-width: 100%; padding: 10px 12px; cursor: pointer; }
input[type="file"] { max-width: 100%; padding: 8px 10px; color: var(--text-dim); }
input[type="file"]::file-selector-button {
  margin-right: 10px;
  padding: 5px 12px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-elev-2);
  color: var(--text);
  font: inherit;
  font-size: var(--fs-xs);
  cursor: pointer;
  transition: border-color .2s;
}
input[type="file"]::file-selector-button:hover { border-color: var(--border-strong); }
input[type="checkbox"] { accent-color: var(--brand-1); width: auto; }

label.opt { display: inline-flex; align-items: center; gap: 8px; font-size: var(--fs-sm); color: var(--text-dim); }

/* iOS 上小于 16px 的输入框聚焦会放大页面 */
@media (max-width: 640px) {
  textarea, input[type="text"], input[type="number"], select { font-size: 16px; }
}

/* ===== 按钮 ===== */
.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 9px 17px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-elev-2);
  color: var(--text);
  font: inherit;
  font-size: var(--fs-sm);
  font-weight: 500;
  cursor: pointer;
  overflow: hidden;
  isolation: isolate;
  -webkit-tap-highlight-color: transparent;
  transition: transform .2s cubic-bezier(.2,.8,.3,1), box-shadow .3s, border-color .2s, background .2s, color .2s;
}
.btn::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background: linear-gradient(105deg, transparent 34%, rgba(255, 255, 255, 0.20) 50%, transparent 66%);
  transform: translateX(-130%);
  transition: transform .65s ease;
}
.btn:hover { transform: translateY(-2px); border-color: var(--border-strong); }
.btn:hover::after { transform: translateX(130%); }
.btn:active { transform: translateY(0) scale(.98); }
.btn:focus-visible { outline: 2px solid var(--accent-line); outline-offset: 2px; }

.btn.primary {
  border-color: transparent;
  color: #fff;
  font-weight: 500;
  padding: 10px 20px;
  background-image: linear-gradient(100deg, var(--brand-1), var(--brand-2) 55%, var(--brand-3));
  background-size: 170% auto;
  box-shadow: 0 12px 28px -16px color-mix(in srgb, var(--brand-1) 90%, transparent);
}
.btn.primary:hover {
  background-position: 100% center;
  box-shadow: 0 18px 36px -16px color-mix(in srgb, var(--brand-2) 90%, transparent);
}

.btn.tiny { font-size: var(--fs-xs); padding: 6px 13px; }
.btn.copied { border-color: transparent; color: #fff; background-image: linear-gradient(100deg, var(--ok), #2ea043); }

/* ===== 布局小工具 ===== */
.row { display: flex; flex-wrap: wrap; gap: 10px; align-items: center; }
.row.wrap-end { justify-content: flex-end; }
.opts { display: flex; flex-wrap: wrap; gap: 10px 16px; align-items: center; }
.opts > * { flex: none; }
.io { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); }
.kv { display: grid; gap: 4px; font-size: var(--fs-sm); }
.kv .k { color: var(--text-faint); font-size: var(--fs-xs); }
.mono { font-family: var(--mono); }

/* ===== 提示信息 ===== */
.msg {
  display: block;
  margin-top: 10px;
  padding: 9px 13px;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--bg-elev-2);
  font-size: var(--fs-sm);
  color: var(--text-dim);
}
.msg.err  { color: var(--err);  border-color: color-mix(in srgb, var(--err) 35%, transparent);  background: color-mix(in srgb, var(--err) 10%, transparent); }
.msg.warn { color: var(--warn); border-color: color-mix(in srgb, var(--warn) 35%, transparent); background: color-mix(in srgb, var(--warn) 10%, transparent); }
.msg.ok   { color: var(--ok);   border-color: color-mix(in srgb, var(--ok) 35%, transparent);   background: color-mix(in srgb, var(--ok) 10%, transparent); }

/* ===== 结果统计 ===== */
.stat-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(112px, 1fr));
  gap: 10px;
  margin-top: 12px;
}
.stat {
  padding: 11px 13px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-elev-2);
  animation: pop .4s cubic-bezier(.2,.9,.3,1.2) both;
}
.stat:nth-child(2) { animation-delay: .05s; }
.stat:nth-child(3) { animation-delay: .1s; }
.stat:nth-child(4) { animation-delay: .15s; }
.stat:nth-child(5) { animation-delay: .2s; }
.stat .k { font-size: var(--fs-xs); color: var(--text-faint); }
.stat .v { font-size: var(--fs-lg); font-weight: 600; font-variant-numeric: tabular-nums; letter-spacing: -0.01em; }

@keyframes pop { from { opacity: 0; transform: translateY(8px) scale(.96); } to { opacity: 1; transform: none; } }

/* ===== 输出框 ===== */
.out {
  padding: 13px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg-inset);
  font-family: var(--mono);
  font-size: var(--fs-sm);
  white-space: pre-wrap;
  word-break: break-word;
  overflow: auto;
}
.out.tall { min-height: 180px; }

/* ===== 正文（静态 SEO 段落） ===== */
.prose {
  max-width: 820px;
  margin: 46px auto 0;
}
.prose h2 {
  position: relative;
  margin: 0 0 16px;
  padding-bottom: 10px;
  font-size: var(--fs-xl);
  font-weight: 600;
  letter-spacing: -0.02em;
}
.prose h2::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 54px; height: 2px;
  border-radius: 2px;
  background: linear-gradient(90deg, var(--brand-1), var(--brand-2), var(--brand-3));
}
.prose h3 { margin: 22px 0 6px; font-size: var(--fs-md); font-weight: 600; }
.prose p { margin: 0 0 12px; color: var(--text-dim); }
.prose p strong { color: var(--text); font-weight: 500; }
.prose ol, .prose ul { margin: 0 0 12px; padding-left: 22px; color: var(--text-dim); }
.prose li { margin-bottom: 7px; }
.prose li strong { color: var(--text); font-weight: 500; }
.prose code {
  font-family: var(--mono);
  font-size: var(--fs-xs);
  padding: 2px 6px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg-elev-2);
  color: var(--text);
  white-space: nowrap;
}

.callout {
  padding: 14px 16px;
  border: 1px solid color-mix(in srgb, var(--brand-1) 30%, transparent);
  border-left-width: 3px;
  border-radius: 4px var(--radius-sm) var(--radius-sm) 4px;
  background: color-mix(in srgb, var(--brand-1) 9%, transparent);
  color: var(--text-dim);
}
.callout strong { color: var(--text); font-weight: 500; }
.callout code { background: color-mix(in srgb, var(--bg) 40%, transparent); }

/* ===== 页脚 ===== */
.footer {
  position: relative;
  padding: 22px 20px 30px;
  text-align: center;
  font-size: var(--fs-xs);
  color: var(--text-faint);
}
.footer::before {
  content: "";
  position: absolute;
  inset: 0 0 auto 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border-strong), transparent);
}

/* ===== 复制成功提示 ===== */
.toast {
  position: fixed;
  left: 50%;
  bottom: 30px;
  z-index: 60;
  padding: 10px 20px;
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  backdrop-filter: blur(16px) saturate(170%);
  box-shadow: var(--shadow);
  color: var(--text);
  font-size: var(--fs-sm);
  opacity: 0;
  transform: translate(-50%, 14px) scale(.96);
  pointer-events: none;
  transition: opacity .28s ease, transform .38s cubic-bezier(.2,.9,.3,1.2);
}
.toast.show { opacity: 1; transform: translate(-50%, 0) scale(1); }
.toast:empty { display: none; }

/* ===== 入场动效 ===== */
@keyframes rise {
  from { opacity: 0; transform: translateY(20px) scale(.994); }
  to   { opacity: 1; transform: none; }
}

@media (prefers-reduced-motion: no-preference) {
  .hero      { animation: rise .75s cubic-bezier(.22,.85,.28,1) both; }
  .tool-grid { animation: rise .75s .1s cubic-bezier(.22,.85,.28,1) both; }
  .prose     { animation: rise .8s .14s cubic-bezier(.22,.85,.28,1) both; }
}

/* ===== 滚动条 ===== */
* { scrollbar-width: thin; scrollbar-color: var(--border-strong) transparent; }
::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-thumb {
  background: var(--border-strong);
  border: 3px solid transparent;
  background-clip: content-box;
  border-radius: 999px;
}
::-webkit-scrollbar-thumb:hover { background: color-mix(in srgb, var(--brand-1) 60%, transparent); background-clip: content-box; }

/* ===== 响应式 ===== */
@media (max-width: 640px) {
  .app { padding: 16px 14px 44px; }
  .hero { padding-top: 10px; }
  .hero p { font-size: var(--fs-sm); }
  .prose { margin-top: 34px; }
  .panel { padding: 15px; border-radius: 16px; }
  .row .btn { flex: 1 1 auto; justify-content: center; }
}

@media (max-width: 420px) {
  .brand-text { display: none; }
}

/* ===== 无障碍：关闭动效 ===== */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
  }
}

/* ==========================================================================
   效果预览：模态框 + 白纸文档 + 公式排版
   ========================================================================== */

body.preview-open { overflow: hidden; }

.preview-backdrop {
  position: fixed;
  inset: 0;
  z-index: 80;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: clamp(10px, 3vw, 30px);
  background: color-mix(in srgb, #05070c 60%, transparent);
  backdrop-filter: blur(6px);
  animation: fade .22s ease both;
}

@keyframes fade { from { opacity: 0; } to { opacity: 1; } }

.preview-dialog {
  display: flex;
  flex-direction: column;
  width: min(900px, 100%);
  height: min(88vh, 100%);
  border: 1px solid var(--border-strong);
  border-radius: var(--radius);
  background: color-mix(in srgb, var(--bg) 94%, #000);
  box-shadow: 0 40px 90px -50px #000;
  overflow: hidden;
  animation: rise .32s cubic-bezier(.22,.85,.28,1) both;
}

.preview-head {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  padding: 14px 16px;
  border-bottom: 1px solid var(--border);
}
.preview-title { font-size: var(--fs-md); font-weight: 600; }
.preview-sub { margin-top: 2px; font-size: var(--fs-xs); color: var(--text-faint); }

.preview-close {
  flex: none;
  margin-left: auto;
  width: 32px; height: 32px;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: var(--bg-elev);
  color: var(--text-dim);
  font-size: var(--fs-sm);
  cursor: pointer;
  transition: color .2s, border-color .2s, transform .3s;
}
.preview-close:hover { color: var(--text); border-color: var(--border-strong); transform: rotate(90deg); }

.preview-body {
  flex: 1;
  overflow: auto;
  padding: clamp(12px, 2.4vw, 24px);
  background: color-mix(in srgb, #000 20%, transparent);
}
.preview-empty { padding: 44px 10px; text-align: center; color: var(--text-faint); font-size: var(--fs-sm); }

.preview-foot {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 12px 16px;
  border-top: 1px solid var(--border);
}
.preview-note { font-size: var(--fs-xs); color: var(--text-faint); }
.preview-gap { flex: 1; }

/* 白纸：固定浅色，模拟 Word 页面，不跟随站点主题 */
.preview-paper {
  max-width: 760px;
  min-height: 60vh;
  margin: 0 auto;
  padding: clamp(20px, 4vw, 44px) clamp(18px, 4vw, 50px);
  border-radius: 6px;
  background: #fff;
  color: #1b1b1f;
  font-family: "Times New Roman", "Songti SC", "SimSun", var(--sans);
  line-height: 1.75;
  box-shadow: 0 20px 50px -30px rgba(0, 0, 0, .8);
}
.preview-paper .doc-quote > .doc > * { margin: 0; }

/* 文档排版 */
.doc > * + * { margin-top: .62em; }
.doc h1, .doc h2, .doc h3, .doc h4, .doc h5, .doc h6 { margin: .9em 0 0; line-height: 1.3; }
.doc h1 { font-size: 1.75em; }
.doc h2 { font-size: 1.42em; }
.doc h3 { font-size: 1.2em; }
.doc h4, .doc h5, .doc h6 { font-size: 1.04em; }
.doc p, .doc-p { margin: 0; text-align: justify; }
.doc-hr { margin: 1.2em 0; border: 0; border-top: 1px solid #d6d6de; }
.doc-list { margin: 0; padding-left: 1.6em; }
.doc-item { margin: .18em 0; }
.doc-item.task { list-style: none; margin-left: -1.35em; }
.doc-task { display: inline-block; width: 1.25em; color: #4b5563; }
.doc-quote {
  margin: 0;
  padding: .5em 0 .5em 1em;
  border-left: 3px solid #c9ccd6;
  color: #4b5563;
}
.doc-code {
  margin: 0;
  padding: .8em 1em;
  border-radius: 8px;
  background: #f4f5f8;
  color: #24292f;
  font-family: var(--mono);
  font-size: .86em;
  line-height: 1.6;
  white-space: pre-wrap;
  word-break: break-word;
}
.doc-table { width: 100%; border-collapse: collapse; font-size: .96em; }
.doc-th, .doc-td { padding: .4em .6em; border: 1px solid #d6d6de; }
.doc-th { background: #f4f5f8; font-weight: 600; }
.doc-table .a-left, .doc .a-left { text-align: left; }
.doc-table .a-center, .doc .a-center { text-align: center; }
.doc-table .a-right, .doc .a-right { text-align: right; }

/* 行内元素 */
.r-b { font-weight: 700; }
.r-i { font-style: italic; }
.r-del { text-decoration: line-through; }
.r { overflow-wrap: anywhere; }
.r-code {
  padding: .1em .35em;
  border-radius: 4px;
  background: #f0f1f5;
  font-family: var(--mono);
  font-size: .88em;
}
.r-link { color: #1a56db; text-decoration: underline; }
.r-img { color: #6b7280; font-style: italic; }

/* 公式：分数是上下两层、根号带上划线、求和号带上下限 */
.m-math, .m-math-display {
  font-family: "Cambria Math", "Latin Modern Math", "Times New Roman", var(--sans);
}
.m-g { display: inline; }
.m-r { font-style: italic; }
.m-r.up, .m-func { font-style: normal; }
.m-func { margin-right: .12em; }

.m-frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  vertical-align: middle;
  margin: 0 .12em;
  font-size: .96em;
  line-height: 1.16;
}
.m-num, .m-den { padding: 0 .25em; }
.m-den { border-top: 1px solid currentColor; }
.m-frac.nobar .m-den { border-top: 0; }

.m-script { display: inline-flex; align-items: flex-start; }
.m-scripts {
  display: inline-flex;
  flex-direction: column;
  align-items: flex-start;
  margin-left: .06em;
  font-size: .72em;
  line-height: 1.12;
}
.m-sup, .m-sub { display: block; }

/* 只挂一个上下标时走这里：行内元素 + vertical-align，由浏览器按字体度量定位（跟 <sub>/<sup> 一样）。
   上面那套 flex 竖列只适合「上下标同时存在」的情况。 */
.m-script1 { display: inline; }
.m-script1 > .m-sup, .m-script1 > .m-sub { display: inline-block; font-size: .72em; line-height: 1; }
.m-script1 > .m-sup { vertical-align: super; }
.m-script1 > .m-sub { vertical-align: sub; }

/* 积分号这类上下限跟在右侧的：只有下标时往下压一档，别浮在积分号中部 */
.m-nary > .m-scripts.only-sub { position: relative; top: .56em; }

.m-under { display: inline-flex; flex-direction: column; align-items: center; vertical-align: middle; }
.m-under.above .m-lim { order: -1; }
.m-lim { font-size: .72em; line-height: 1.12; }
.m-base { padding: 0 .05em; }

.m-nary { display: inline-flex; align-items: center; vertical-align: middle; gap: .06em; }
.m-opstack { display: inline-flex; flex-direction: column; align-items: center; }
.m-op { font-size: 1.5em; line-height: .92; }
.m-op.int { font-size: 1.32em; }
.m-nary-body { padding-left: .08em; }

.m-rad { display: inline-flex; align-items: stretch; }
.m-rad-deg { align-self: flex-start; margin-right: -.4em; font-size: .6em; line-height: 1; }
.m-rad-sym { font-size: 1.05em; line-height: 1; }
.m-rad-body {
  margin-left: -.05em;
  padding: .1em .16em 0 .1em;
  border-top: 1px solid currentColor;
}

.m-delim { display: inline-flex; align-items: center; }
.m-delim-chr { font-size: 1.25em; line-height: 1; }
.m-delim-body { display: inline-flex; align-items: center; padding: 0 .1em; }

.m-bar { display: inline-block; padding: 0 .05em; }
.m-bar.top { border-top: 1px solid currentColor; }
.m-bar.bot { border-bottom: 1px solid currentColor; }

.m-acc { position: relative; display: inline-block; white-space: nowrap; }
.m-acc-chr { margin-left: -.06em; }

.m-groupchr { display: inline-flex; flex-direction: column; align-items: center; }
.m-gc { font-size: .95em; line-height: .6; }
.m-gc-base { padding: 0 .15em; }

.m-matrix { display: inline-flex; flex-direction: column; gap: .28em; vertical-align: middle; }
.m-row { display: inline-flex; gap: .9em; justify-content: center; }
.m-cell { display: inline-block; text-align: center; }
.m-matrix.sep .m-cell + .m-cell {
  padding-left: .7em;
  border-left: 1px solid color-mix(in srgb, currentColor 35%, transparent);
}

.m-eqarr { display: inline-flex; flex-direction: column; gap: .22em; }
.m-eqrow { display: block; }
.m-brk { display: block; height: 0; }
.m-align { display: inline-block; width: .28em; }

.m-math-display { display: block; margin: .85em 0; text-align: center; overflow-x: auto; }

/* 字体样式（\mathbf \mathit \mathbb 等）在网页里的近似 */
.m-g.s-b { font-weight: 700; }
.m-g.s-i { font-style: italic; }
.m-g.s-bi { font-weight: 700; font-style: italic; }
.m-g.s-p { font-style: normal; }
.m-g.f-ss { font-family: var(--sans); }
.m-g.f-tt { font-family: var(--mono); }
.m-g.f-ds, .m-g.f-fr, .m-g.f-sc { font-family: "Cambria Math", "Times New Roman", serif; }

@media (max-width: 640px) {
  .preview-dialog { height: 92vh; }
  .preview-paper { padding: 18px 16px; }
}