CSS 高级选择器

伪类	效果
first-child	🟤⚪⚪⚪⚪⚪
last-child	⚪⚪⚪⚪⚪🟤
nth-child(2)	⚪🟤⚪⚪⚪⚪
nth-child(odd)	🟤⚪🟤⚪🟤⚪
nth-child(even)	⚪🟤⚪🟤⚪🟤
nth-child(n+4)	⚪⚪⚪🟤🟤🟤
nth-child(3n-1)	⚪🟤⚪⚪🟤⚪
nth-child(3n+1)	🟤⚪⚪🟤⚪⚪
nth-child(4n)	⚪⚪⚪🟤⚪⚪