* {
  box-sizing: border-box;
}

html {
  font-size: 16px;
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", Arial, sans-serif;
  color: #1f2937;
  background: #ffffff;
  line-height: 1.75;
}

main {
  min-height: 100vh;
  padding: 48px 20px;
}

article {
  width: 100%;
  max-width: 880px;
  margin: 0 auto;
}

h1 {
  margin: 0 0 32px;
  color: #111827;
  font-size: 32px;
  line-height: 1.3;
  font-weight: 700;
  text-align: center;
}

h2 {
  margin: 36px 0 16px;
  color: #111827;
  font-size: 22px;
  line-height: 1.45;
  font-weight: 650;
}

h3 {
  margin: 28px 0 12px;
  color: #111827;
  font-size: 18px;
  line-height: 1.5;
  font-weight: 650;
}

p {
  margin: 0 0 16px;
  font-size: 16px;
}

span {
  font-size: inherit;
}

a {
  color: #2563eb;
  text-decoration: none;
  word-break: break-word;
}

a:hover {
  text-decoration: underline;
}

ul,
ol {
  margin: 0 0 16px 24px;
  padding: 0;
}

li {
  margin: 0 0 8px;
  font-size: 16px;
}

strong,
b {
  color: #111827;
  font-weight: 650;
}

@media (max-width: 640px) {
  main {
    padding: 32px 16px;
  }

  h1 {
    margin-bottom: 24px;
    font-size: 28px;
  }

  h2 {
    margin-top: 30px;
    font-size: 20px;
  }

  h3 {
    font-size: 17px;
  }

  p,
  li {
    font-size: 15px;
  }
}