/* ============================================================
   算术练习本 · 手写练习本美学
   设计方向：warm paper · ink + crimson · 手写感 · 移动优先
   ============================================================ */

:root {
  /* —— 色彩 —— */
  --paper: #fdfbf6;          /* 米白纸 */
  --paper-line: #d9e7d4;     /* 笔记本横线（淡绿） */
  --ink: #1c1b1a;            /* 墨黑 */
  --ink-soft: #4a4844;
  --crimson: #c8324c;        /* 朱红批改色 */
  --crimson-deep: #8e1f33;
  --accent: #2d5f3f;         /* 深松绿 */
  --bg: #1a1a1a;             /* 屏幕深色背景衬托纸张 */
  --bg-soft: #232323;
  --panel-bg: #1f1d1b;
  --line: #3a3835;
  --muted: #8a857d;
  --gold: #d4a84b;

  /* —— 字体 —— */
  --ff-display: "Noto Serif SC", "Songti SC", serif;
  --ff-hand: "Caveat", "Noto Serif SC", cursive;
  --ff-mono: "JetBrains Mono", "Courier New", monospace;

  /* —— 尺寸 —— */
  --paper-w: 210mm;
  --paper-h: 297mm;
  --topbar-h: 60px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--ff-display);
  background: var(--bg);
  color: #e8e3da;
  line-height: 1.5;
  min-height: 100vh;
  overflow-x: hidden;
}

/* 屏幕背景：细微噪点纹理 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image:
    radial-gradient(circle at 20% 30%, rgba(212,168,75,.04), transparent 50%),
    radial-gradient(circle at 80% 70%, rgba(200,50,76,.03), transparent 50%);
  pointer-events: none;
  z-index: 0;
}

/* ============================================================
   顶部栏
   ============================================================ */
.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--topbar-h);
  background: rgba(26,26,26,.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--line);
  z-index: 100;
}
.topbar-inner {
  max-width: 1400px;
  height: 100%;
  margin: 0 auto;
  padding: 0 16px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
}
.logo { display: flex; align-items: center; gap: 10px; min-width: 0; }
.logo-mark {
  font-family: var(--ff-display);
  font-size: 28px;
  font-weight: 900;
  color: var(--gold);
  line-height: 1;
}
.logo-text h1 {
  font-family: var(--ff-display);
  font-size: 16px;
  font-weight: 900;
  color: #f5f0e6;
  letter-spacing: .02em;
  white-space: nowrap;
}
.logo-text p {
  font-family: var(--ff-mono);
  font-size: 10px;
  color: var(--muted);
  letter-spacing: .08em;
  text-transform: uppercase;
}
.topbar-actions { display: flex; align-items: center; gap: 4px; }

.ghost-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: transparent;
  border: 1px solid transparent;
  color: #c8c2b6;
  padding: 8px 12px;
  border-radius: 10px;
  font-family: var(--ff-display);
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: all .2s;
}
.ghost-btn:hover:not(:disabled) { background: rgba(255,255,255,.06); border-color: var(--line); }
.ghost-btn:disabled { opacity: .35; cursor: not-allowed; }
.ghost-btn svg { flex-shrink: 0; }

.menu-btn {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 4px;
  width: 40px; height: 40px;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 10px;
  cursor: pointer;
  padding: 0 9px;
}
.menu-btn span {
  display: block;
  height: 2px;
  background: #e8e3da;
  border-radius: 2px;
  transition: .25s;
}

/* ============================================================
   设置面板（桌面：左侧固定栏 / 移动：抽屉）
   ============================================================ */
.panel {
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  bottom: 0;
  width: 300px;
  background: var(--panel-bg);
  border-right: 1px solid var(--line);
  overflow-y: auto;
  z-index: 90;
  transition: transform .3s cubic-bezier(.4,0,.2,1);
}
.panel-head {
  position: sticky;
  top: 0;
  background: var(--panel-bg);
  padding: 18px 20px 14px;
  border-bottom: 1px solid var(--line);
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 2;
}
.panel-head h2 {
  font-family: var(--ff-display);
  font-size: 15px;
  font-weight: 900;
  color: #f5f0e6;
  letter-spacing: .03em;
}
.panel-close {
  display: none;
  background: transparent;
  border: none;
  color: var(--muted);
  font-size: 26px;
  line-height: 1;
  cursor: pointer;
}

.panel-body { padding: 16px 20px 40px; }

.field { margin-bottom: 22px; }
.field-label {
  display: block;
  font-family: var(--ff-display);
  font-size: 12px;
  font-weight: 700;
  color: var(--muted);
  letter-spacing: .05em;
  margin-bottom: 9px;
  text-transform: uppercase;
}
.field-label .muted { color: var(--gold); font-weight: 400; text-transform: none; letter-spacing: 0; }
.field-hint {
  font-size: 11px;
  color: var(--muted);
  margin-top: 6px;
  font-family: var(--ff-mono);
}

/* 运算类型 chips */
.op-chips { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.op-chip {
  background: transparent;
  border: 1px solid var(--line);
  color: #b8b2a6;
  padding: 11px 8px;
  border-radius: 10px;
  font-family: var(--ff-display);
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  transition: all .15s;
}
.op-chip:hover { border-color: var(--gold); color: #e8e3da; }
.op-chip.active {
  background: var(--gold);
  border-color: var(--gold);
  color: #1a1a1a;
}

/* 分段控件 seg */
.seg {
  display: flex;
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 3px;
  gap: 2px;
}
.seg-btn {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--muted);
  padding: 8px 6px;
  border-radius: 7px;
  font-family: var(--ff-display);
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: all .15s;
}
.seg-btn:hover { color: #e8e3da; }
.seg-btn.active {
  background: var(--ink);
  color: var(--gold);
  box-shadow: 0 1px 3px rgba(0,0,0,.3);
}

/* range slider */
#perPage {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  background: var(--line);
  border-radius: 4px;
  outline: none;
}
#perPage::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 20px; height: 20px;
  background: var(--gold);
  border-radius: 50%;
  cursor: pointer;
  border: 3px solid var(--panel-bg);
  box-shadow: 0 0 0 1px var(--gold);
}
#perPage::-moz-range-thumb {
  width: 20px; height: 20px;
  background: var(--gold);
  border-radius: 50%;
  cursor: pointer;
  border: 3px solid var(--panel-bg);
  box-shadow: 0 0 0 1px var(--gold);
}
.range-ticks {
  display: flex;
  justify-content: space-between;
  font-family: var(--ff-mono);
  font-size: 10px;
  color: var(--muted);
  margin-top: 6px;
}

/* 数字范围输入框 + 快捷按钮 */
.num-input-row {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.num-input {
  width: 90px;
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 10px;
  color: var(--gold);
  font-family: var(--ff-mono);
  font-size: 20px;
  font-weight: 700;
  text-align: center;
  padding: 8px;
  outline: none;
  transition: border-color .15s;
}
.num-input:focus { border-color: var(--gold); }
.num-input::-webkit-inner-spin-button,
.num-input::-webkit-outer-spin-button { -webkit-appearance: none; margin: 0; }
.num-input { -moz-appearance: textfield; }

.quick-btns { display: flex; gap: 5px; flex-wrap: wrap; }
.quick-btn {
  background: transparent;
  border: 1px solid var(--line);
  color: var(--muted);
  font-family: var(--ff-mono);
  font-size: 12px;
  font-weight: 700;
  padding: 6px 11px;
  border-radius: 8px;
  cursor: pointer;
  transition: all .15s;
}
.quick-btn:hover { border-color: var(--gold); color: #e8e3da; }

/* 开关 switch rows */
.switch-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 9px 0;
  font-size: 13px;
  color: #c8c2b6;
  cursor: pointer;
}
.switch {
  position: relative;
  width: 38px; height: 22px;
  -webkit-appearance: none;
  appearance: none;
  background: var(--line);
  border-radius: 22px;
  cursor: pointer;
  transition: .2s;
  flex-shrink: 0;
}
.switch::before {
  content: "";
  position: absolute;
  width: 16px; height: 16px;
  background: #e8e3da;
  border-radius: 50%;
  top: 3px; left: 3px;
  transition: .2s;
}
.switch:checked { background: var(--accent); }
.switch:checked::before { transform: translateX(16px); }

/* 主按钮 */
.primary-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  width: 100%;
  background: var(--crimson);
  color: #fff;
  border: none;
  padding: 14px;
  border-radius: 12px;
  font-family: var(--ff-display);
  font-size: 15px;
  font-weight: 900;
  letter-spacing: .03em;
  cursor: pointer;
  transition: all .2s;
  box-shadow: 0 4px 14px rgba(200,50,76,.3);
}
.primary-btn:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(200,50,76,.4); }
.primary-btn:active { transform: translateY(0); }
.primary-btn.inline { width: auto; padding: 12px 28px; margin-top: 8px; }

/* ============================================================
   遮罩
   ============================================================ */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,.5);
  backdrop-filter: blur(2px);
  z-index: 85;
  opacity: 0;
  animation: fadeIn .2s forwards;
}

/* ============================================================
   主区域
   ============================================================ */
.main {
  margin-left: 300px;
  padding-top: var(--topbar-h);
  min-height: 100vh;
  position: relative;
  z-index: 1;
}

.output {
  padding: 32px 24px 80px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 28px;
}

/* 空状态 */
.empty-state {
  text-align: center;
  padding: 80px 20px;
  max-width: 420px;
}
.empty-mark {
  font-family: var(--ff-mono);
  font-size: 32px;
  color: var(--gold);
  letter-spacing: .3em;
  margin-bottom: 24px;
  opacity: .8;
}
.empty-state h2 {
  font-family: var(--ff-display);
  font-size: 24px;
  font-weight: 900;
  color: #f5f0e6;
  margin-bottom: 10px;
}
.empty-state p {
  color: var(--muted);
  font-size: 14px;
  margin-bottom: 8px;
}

/* ============================================================
   A4 纸张 —— 屏幕所见即打印所得
   ============================================================ */
.paper {
  background: var(--paper);
  width: var(--paper-w);
  min-height: var(--paper-h);
  padding: 24mm 12mm 12mm;  /* 顶部增加留白，让姓名栏往下移 */
  box-shadow: 0 8px 40px rgba(0,0,0,.4), 0 2px 8px rgba(0,0,0,.3);
  position: relative;
  color: var(--ink);
  flex-shrink: 0;
}


/* 纸张保持干净，不加横线纹理（避免与答题线冲突、打印干扰） */
.paper > * { position: relative; }

/* 页眉 */
.paper-header {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  border-bottom: 2px solid var(--ink);
  padding-bottom: 7px;
  margin-bottom: 4px;
  font-family: var(--ff-display);
  font-size: 14px;
  font-weight: 700;
}
.underline-field {
  display: inline-block;
  min-width: 80px;
  border-bottom: 1px solid var(--ink);
}
.paper-title {
  text-align: center;
  font-family: var(--ff-display);
  font-size: 20px;
  font-weight: 900;
  letter-spacing: .08em;
  margin: 60px 0 34px;
  color: var(--ink);
}
.paper-title .page-no {
  font-family: var(--ff-mono);
  font-size: 12px;
  font-weight: 400;
  color: var(--ink-soft);
  letter-spacing: 0;
}

/* 页脚批改信息栏（家长/老师用） */
.paper-footer {
  margin-top: 16px;
  padding-top: 8px;
  border-top: 1px dashed var(--ink-soft);
  text-align: center;
  font-family: var(--ff-mono);
  font-size: 11px;
  font-weight: 600;
  color: var(--ink-soft);
  letter-spacing: .03em;
}

/* ============================================================
   横式题目 —— 操作数固定宽度右对齐，运算符永远居中
   ============================================================ */
.grid-horizontal {
  display: grid;
  /* 列数由 app.js 内联设置，默认 4 列 */
  grid-template-columns: repeat(4, 1fr);
  gap: 14px 18px;
}
.q-h {
  font-family: var(--ff-mono);
  font-size: 13px;
  font-weight: 600;
  white-space: nowrap;
  min-width: 0;
  padding: 6px 0;
  color: var(--ink);
  display: flex;
  align-items: baseline;
}
.q-h .num {
  color: var(--crimson);
  font-size: 10px;
  font-weight: 700;
  margin-right: 5px;
  opacity: .7;
  flex-shrink: 0;
}
.q-h .opd {
  width: 28px;
  text-align: right;
  flex-shrink: 0;
}
.q-h .sign {
  width: 18px;
  text-align: center;
  flex-shrink: 0;
  font-weight: 700;
  font-family: "Segoe UI Symbol", "Cambria Math", "Times New Roman", serif;  /* 比例字体，符号视觉居中 */
  font-size: 15px;
  position: relative;
  top: -1px;            /* 微调符号垂直位置，对齐数字中线 */
}
.q-h .eq {
  width: 14px;
  text-align: center;
  flex-shrink: 0;
  margin-right: 2px;
}
/* 答案区：纯空白，无下划线（显示答案时填入数字） */
.q-h .blank {
  width: 42px;
  flex-shrink: 0;
  text-align: center;
}
/* 答案区：默认隐藏答案，body.show-ans 时显示 */
.ans-wrap {
  display: none;
  color: var(--crimson-deep);
  font-weight: 700;
}
body.show-ans .ans-wrap {
  display: inline;
}

/* ============================================================
   竖式题目 —— 题号(左上) + 运算符(垂直居中) + 数字列(右对齐)
   ============================================================ */
.grid-vertical {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 64px 24px;
}
.q-v {
  font-family: var(--ff-mono);
  font-size: 18px;
  font-weight: 600;
  display: flex;
  align-items: stretch;
  color: var(--ink);
  position: relative;
  padding-top: 18px;       /* 给题号留位置 */
}
.q-v .num {
  color: var(--crimson);
  font-size: 12px;
  font-weight: 700;
  position: absolute;
  left: 0; top: 0;
  opacity: .75;
}
.q-v .op-col {
  display: flex;
  align-items: center;     /* 运算符垂直居中对齐两个数字行中间 */
  padding-right: 8px;
  font-weight: 700;
}
.q-v .digits {
  display: flex;
  flex-direction: column;
  line-height: 1.5;
}
.q-v .row-r { text-align: right; padding-right: 2px; }
.q-v .line {
  display: block;
  height: 0;
  border-top: 1.5px solid var(--ink);
  margin: 3px 0;
}
.q-v .ans-wrap {
  display: none;          /* 默认隐藏，由 body.show-ans 覆盖 */
  text-align: right;
  padding-top: 6px;
}
body.show-ans .q-v .ans-wrap {
  display: block;
}

/* 题目入场动画 */
@keyframes inkIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}
.q-h, .q-v { animation: inkIn .25s ease-out both; }

/* ============================================================
   响应式：平板/手机（≤1024px）—— A4 整体缩放预览
   ============================================================ */
@media (max-width: 1024px) {
  .main { margin-left: 0; }
  .menu-btn { display: flex; }
  .panel-close { display: block; }
  .panel {
    width: 320px;
    transform: translateX(-100%);
    box-shadow: 4px 0 30px rgba(0,0,0,.5);
  }
  .panel.open { transform: translateX(0); }
  .panel[aria-hidden="true"] { transform: translateX(-100%); }

  .logo-text p { display: none; }
  .ghost-btn .label { display: none; }
  .ghost-btn { padding: 8px 10px; }

  .output { padding: 12px 0 40px; gap: 14px; }

  /* 窄屏：A4 纸张保持原始尺寸，由 JS updateScale() 整体缩放预览 */
  /* 打印时不受影响，仍为完整 A4 单页 */
  .paper-stage {
    width: 100%;
    margin: 0 auto;
    display: flex;
    justify-content: center;
  }
  .paper-scaler {
    /* transform / width 由 JS 设置 */
    display: flex;
    flex-direction: column;
    align-items: center;
  }
}

@media (max-width: 480px) {
  .panel { width: 88%; }
  .menu-btn { width: 36px; height: 36px; }
}

/* ============================================================
   打印样式
   ============================================================ */
@page {
  size: A4;
  margin: 12mm;
  /* 以下属性可以尽可能清除浏览器默认的页眉页脚区域 */
  margin-top: 0;
  margin-bottom: 0;
}


@media print {
  html, body { background: #fff; }
  body::before, .topbar, .panel, .overlay, .menu-btn { display: none !important; }

  .main { margin: 0; padding: 0; }
  .output { padding: 0; gap: 0; display: block; }

  .empty-state { display: none; }

  /* 关键：还原手机端的缩放，打印必须用原始 A4 尺寸 */
  .paper-stage {
    width: auto !important;
    height: auto !important;
    overflow: visible !important;
    display: block !important;
  }
  .paper-scaler {
    transform: none !important;
    width: auto !important;
    display: block !important;
  }

  .paper {
    width: 210mm;          /* 打印强制 A4 宽度，不受手机窄视口影响 */
    min-height: auto;
    margin: 0;
    background: #fff !important;   /* 打印用纯白纸，不印米黄底色 */
    /* 保留 padding 作为纸内边距，让内容不贴边 */
    box-shadow: none;
    page-break-after: always;
    break-after: page;
  }
  .paper:last-child { page-break-after: auto; break-after: auto; }

  .ans-wrap { color: var(--crimson-deep); }
}

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

/* 试卷保持干净，无底部装饰 */