@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;700&family=Outfit:wght@400;500;600;700&display=swap');

:root {
  --bg-primary: #FAF6F0; /* 护眼象牙白 */
  --bg-panel: #FFFFFF;
  --border-light: #E6DFD5;
  --text-dark: #4A433D;
  --text-muted: #8F857B;
  --accent-coral: #C88C6B; /* 珊瑚橙 */
  --accent-green: #8EA68B; /* 森绿 */
  --accent-blue: #6B9EC8;  /* 科技蓝 */
  
  --font-ui: 'Outfit', 'Inter', system-ui, -apple-system, BlinkMacSystemFont, sans-serif;
  --font-mono: 'Courier New', Courier, monospace;
}

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

body {
  background-color: var(--bg-primary);
  color: var(--text-dark);
  font-family: var(--font-ui);
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  padding-bottom: 3rem;
}

/* 配置面板样式 */
.config-panel {
  width: 100%;
  max-width: 794px;
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  border-radius: 16px;
  padding: 1.5rem;
  margin: 1.5rem 0;
  box-shadow: 0 4px 20px rgba(74, 67, 61, 0.05);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
}

.header-title h1 {
  font-size: 1.5rem;
  color: var(--accent-coral);
  font-weight: 700;
  letter-spacing: 0.05em;
}
.header-title p {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.config-options {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 1.25rem;
  border-top: 1px solid var(--border-light);
  padding-top: 1rem;
}

.config-group {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.config-label {
  font-size: 0.85rem;
  font-weight: bold;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.radio-group, .checkbox-group {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
  font-size: 0.9rem;
}
.radio-group label, .checkbox-group label {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  cursor: pointer;
  user-select: none;
}

select {
  background: var(--bg-primary);
  border: 1px solid var(--border-light);
  border-radius: 6px;
  padding: 0.45rem;
  color: var(--text-dark);
  font-family: var(--font-ui);
  font-size: 0.9rem;
  outline: none;
  cursor: pointer;
}

/* 动作按钮区 */
.actions-bar {
  display: flex;
  gap: 0.75rem;
  justify-content: flex-end;
  border-top: 1px solid var(--border-light);
  padding-top: 1rem;
}

.btn {
  border: none;
  padding: 0.6rem 1.25rem;
  border-radius: 8px;
  font-family: var(--font-ui);
  font-weight: 600;
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.15s ease;
}
.btn-primary { background: var(--accent-coral); color: white; }
.btn-primary:hover { opacity: 0.9; transform: translateY(-1px); }
.btn-secondary { background: var(--accent-green); color: white; }
.btn-secondary:hover { opacity: 0.9; transform: translateY(-1px); }
.btn-accent { background: var(--accent-blue); color: white; }
.btn-accent:hover { opacity: 0.9; transform: translateY(-1px); }
.btn-pdf { background: #9B8EA6; color: white; }
.btn-pdf:hover { opacity: 0.9; transform: translateY(-1px); }

/* A4 练习纸容器 */
.preview-area {
  display: flex;
  justify-content: center;
  width: 100%;
}

.sheet-container {
  width: 794px; /* 标准 A4 像素宽度 */
  height: 1123px; /* 标准 A4 像素高度 */
  background: #FFFFFF;
  border: 1px solid #D1C9BE;
  border-radius: 4px;
  box-shadow: 0 12px 36px rgba(74, 67, 61, 0.08);
  padding: 4.5rem 3.5rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  box-sizing: border-box;
  position: relative;
}

.sheet-header {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
  align-items: center;
  border-bottom: 2px double var(--border-light);
  padding-bottom: 1.5rem;
  margin-bottom: 2rem;
}
.sheet-header h2 {
  font-size: 2rem;
  letter-spacing: 0.3em;
  color: #332E2A;
  font-weight: 700;
}
.student-info {
  width: 100%;
  display: flex;
  justify-content: space-between;
  font-size: 0.95rem;
  color: #5C544E;
  font-weight: 500;
}
.student-info span {
  white-space: nowrap;
}

/* 算式网格布局 */
.sheet-grid {
  display: grid;
  grid-template-columns: 1fr 1px 1fr 1px 1fr 1px 1fr;
  gap: 0 1.5rem;
  flex-grow: 1;
  margin-bottom: 2rem;
  align-content: space-between;
}

/* 每一列内部容器 */
.grid-col {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  height: 100%;
  min-height: 750px;
}

/* 列分隔线 */
.grid-divider {
  border-left: 1px dashed var(--border-light);
  height: 100%;
}

/* 每一个算式算子对齐样式 */
.formula-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  width: 100%;
  white-space: nowrap;
  font-family: var(--font-mono);
  font-size: 1.15rem;
  font-weight: 700;
  color: #2C2724;
  line-height: 1.8;
}

.formula-expr {
  white-space: nowrap;
}

.formula-ans {
  white-space: nowrap;
}

/* 答案与书写框样式：始终占用 2.5rem 宽度作为留白，不画下划线 */
.ans-val {
  display: inline-block;
  width: 2.5rem;
  text-align: left;
}

/* 答案显隐控制：默认隐藏答案，当带 .show-answers 类时显示答案结果 */
.sheet-container:not(.show-answers) .ans-val {
  visibility: hidden;
}
.sheet-container.show-answers .ans-val {
  visibility: visible;
  color: var(--accent-coral); /* 答案显示为淡橙色区分 */
}

.sheet-footer {
  text-align: center;
  font-size: 0.8rem;
  color: #AEA59A;
  border-top: 1px dashed var(--border-light);
  padding-top: 1rem;
  margin-top: auto;
  display: flex;
  justify-content: space-between;
}

/* 顶部页签导航栏 */
.nav-tabs {
  display: flex;
  gap: 0.75rem;
  margin-top: 1.5rem;
  width: 100%;
  max-width: 794px;
  justify-content: center;
}
.nav-tab {
  text-decoration: none;
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.95rem;
  padding: 0.5rem 1.5rem;
  border-radius: 20px;
  background: var(--bg-panel);
  border: 1px solid var(--border-light);
  transition: all 0.2s ease;
  box-shadow: 0 2px 8px rgba(74, 67, 61, 0.02);
}
.nav-tab:hover {
  color: var(--accent-coral);
  border-color: var(--accent-coral);
  transform: translateY(-1px);
}
.nav-tab.active {
  color: #FFFFFF;
  background: var(--accent-coral);
  border-color: var(--accent-coral);
  box-shadow: 0 4px 12px rgba(200, 140, 107, 0.2);
}

/* 元角分专用样式 */
.sheet-grid.col-2 {
  grid-template-columns: 1fr 1px 1fr;
  gap: 0 2rem;
}
.currency-sheet .formula-row.row-left {
  justify-content: flex-start;
  gap: 0.1rem;
  letter-spacing: 0.01em;
  font-size: 0.95rem;
  line-height: 1.5;
}
.currency-sheet .ans-val {
  text-align: center;
  width: 1.4rem;
  font-weight: 700;
  border-bottom: 1px solid var(--border-light);
  margin: 0 0.1rem;
}
.sheet-container.show-answers.currency-sheet .ans-val {
  border-bottom-color: rgba(200, 140, 107, 0.3);
}

/* PDF 渲染专用样式覆盖 */
.rendering-pdf .sheet-container {
  border: none !important;
  box-shadow: none !important;
  border-radius: 0 !important;
  margin: 0 !important;
  width: 794px !important;
  height: 1123px !important;
}

/* ===== A4 打印优化媒体查询 ===== */
@media print {
  body {
    background: #FFFFFF !important;
    padding: 0;
    margin: 0;
  }
  .config-panel, .nav-tabs {
    display: none !important;
  }
  .sheet-container {
    width: 100% !important;
    height: 100vh !important;
    border: none !important;
    box-shadow: none !important;
    padding: 2.5rem 2rem !important; /* 打印边距适当紧凑 */
    margin: 0 !important;
  }
}