* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg, #f5f7fa);
  font-family: "Microsoft YaHei", Arial, sans-serif;
  color: var(--text, #333);
  transition: all 0.3s;
}

body.dark {
  --bg: #121212;
  --card: #1e1e1e;
  --text: #eaeaea;
  --border: #333;
  --primary: #4096ff;
  --result: #1f3a5f;
}

.app {
  max-width: 900px;
  margin: auto;
  padding: 16px;
}

h1 {
  text-align: center;
  margin-bottom: 24px;
}

.card {
  background: var(--card, #fff);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 20px;
}

.card h2 {
  margin-bottom: 16px;
  border-left: 4px solid var(--primary, #1677ff);
  padding-left: 10px;
}

/* 核心布局 */
.form-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr); /* 电脑端每行 2 个 */
  gap: 14px 20px;
}

.form-item {
  display: flex;
  align-items: center;
}

.form-item label {
  width: 150px;
  font-weight: 600;
  flex-shrink: 0;
}

.form-item input {
  flex: 1;
  padding: 10px;
  border-radius: 6px;
  border: 1px solid var(--border, #d9d9d9);
  background: var(--card, #fff);
  color: var(--text, #333);
}

/* 按钮效果 */
.calc-btn, .theme-btn {
  border-radius: 10px;
  cursor: pointer;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
  transition: all 0.15s ease-in-out;
}

.calc-btn {
  width: 100%;
  padding: 14px;
  font-size: 16px;
  background: var(--primary, #1677ff);
  color: #fff;
  border: none;
}

.calc-btn:hover {
  filter: brightness(1.05);
}

.calc-btn:active {
  transform: scale(0.96);
  filter: brightness(0.95);
}

.theme-btn {
  background: none;
  border: 1px solid var(--border, #d9d9d9);
  padding: 6px 10px;
  color: var(--text, #333);
}

.theme-btn:hover {
  filter: brightness(1.1);
}

.theme-btn:active {
  transform: scale(0.96);
}

/* 结果 */
.result {
  margin-top: 20px;
  background: var(--result, #e6f4ff);
  padding: 16px;
  border-radius: 10px;
}

/* 手机适配 */
@media (max-width: 768px) {
  .form-grid {
    grid-template-columns: 1fr; /* 手机每行 1 个 */
  }

  .form-item {
    flex-direction: column;
    align-items: stretch;
  }

  .form-item label {
    width: auto;
    margin-bottom: 6px;
  }
}
/* 销售单价（含税）红色显示 */
.result strong {
  color: #ff4d4f; /* 红色 */
}

/* 深色模式下稍亮红色 */
body.dark .result strong {
  color: #ff7875;
}