Flexbox 练习和总结

练习地址： http://flexboxfroggy.com/

Welcome to Flexbox Froggy, a game where you help Froggy and friends by writing CSS code! Guide this frog to the lilypad on the right by using the justify-content property, which aligns items horizontally and accepts the following values:

• flex-start: Items align to the left side of the container.
• flex-end: Items align to the right side of the container.
• center: Items align at the center of the container.
• space-between: Items display with equal spacing between them.
• space-around: Items display with equal spacing around them.

Help all three frogs find their lilypads just by using justify-content. This time, the lilypads have lots of space all around them.

If you find yourself forgetting the possible values for a property, you can hover over the property name to view them. Try hovering over justify-content.

#pond {
  display: flex;
  justify-content: space-around;
}

Now the lilypads on the edges have drifted to the shore, increasing the space between them. Use justify-content. This time, the lilypads have equal spacing between them.

#pond {
  display: flex;
  justify-content: space-between;
}

Now use align-items to help the frogs get to the bottom of the pond. This CSS property aligns items vertically and accepts the following values:

• flex-start: Items align to the top of the container.
• flex-end: Items align to the bottom of the container.
• center: Items align at the vertical center of the container.
• baseline: Items display at the baseline of the container.
• stretch: Items are stretched to fit the container.

#pond {
  display: flex;
  align-items: flex-end;
}

The frogs need to get in the same order as their lilypads using flex-direction. This CSS property defines the direction items are placed in the container, and accepts the following values:

• row: Items are placed the same as the text direction.
• row-reverse: Items are placed opposite to the text direction.
• column: Items are placed top to bottom.
• column-reverse: Items are placed bottom to top.

#pond {
  display: flex;
  flex-direction: row-reverse; 
}

Sometimes reversing the row or column order of a container is not enough. In these cases, we can apply the order property to individual items. By default, items have a value of 0, but we can use this property to set it to a positive or negative integer value.

Use the order property to reorder the frogs according to their lilypads.

#pond {
  display: flex;
}

.yellow {
  order: 1
}

Oh no! The frogs are all squeezed onto a single row of lilypads. Spread them out using the flex-wrap property, which accepts the following values:

• nowrap: Every item is fit to a single line.
• wrap: Items wrap around to additional lines.
• wrap-reverse: Items wrap around to additional lines in reverse.

#pond {
  display: flex;
  flex-wrap: wrap;
}

The two properties flex-direction and flex-wrap are used so often together that the shorthand property flex-flow was created to combine them. This shorthand property accepts the value of one of the two properties separated by a space.

For example, you can use flex-flow: row wrap to set rows and wrap them.

Try using flex-flow to repeat the previous level.

#pond {
  display: flex;
  flex-flow: column wrap;
}

The frogs are spread all over the pond, but the lilypads are bunched at the top. You can use align-content to set how multiple lines are spaced apart from each other. This property takes the following values:

• flex-start: Lines are packed at the top of the container.
• flex-end: Lines are packed at the bottom of the container.
• center: Lines are packed at the vertical center of the container.
• space-between: Lines display with equal spacing between them.
• space-around: Lines display with equal spacing around them.
• stretch: Lines are stretched to fit the container.

This can be confusing, but align-content determines the spacing between lines, while align-items determines how the items as a whole are aligned within the container. When there is only one line, align-content has no effect.

#pond {
  display: flex;
  flex-wrap: wrap;
  align-content: flex-start
}