Flex

flex:1

key：relative to rest of
- flex-grow   A number specifying how much the item will grow relative to the rest of the flexible items.
- flex-shrink  A number specifying how much the item will shrink relative to the rest of the flexible items
- flex-basis  The length of the item. Legal values: "auto", "inherit", or a number followed by "%", "px", "em" or any other length unit.
so flex：1 equalflex： 1 1 0n（where n is a length unit）