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13.4 CSS Animations

CSS allows animation of HTML elements without using JavaScript or Flash!

In this chapter you will learn about the following properties:

• @keyframes
• animation-name
• animation-duration
• animation-delay
• animation-iteration-count
• animation-direction
• animation-timing-function
• animation-fill-mode
• animation

Browser Support for Animations

The numbers in the table specify the first browser version that fully supports the property.

Property
@keyframes	43.0	10.0	16.0	9.0	30.0
animation-name	43.0	10.0	16.0	9.0	30.0
animation-duration	43.0	10.0	16.0	9.0	30.0
animation-delay	43.0	10.0	16.0	9.0	30.0
animation-iteration-count	43.0	10.0	16.0	9.0	30.0
animation-direction	43.0	10.0	16.0	9.0	30.0
animation-timing-function	43.0	10.0	16.0	9.0	30.0
animation-fill-mode	43.0	10.0	16.0	9.0	30.0
animation	43.0	10.0	16.0	9.0	30.0

What are CSS Animations?

An animation lets an element gradually change from one style to another. You can change as many CSS properties you want, as many times you want. To use CSS animation, you must first specify some keyframes for the animation. Keyframes hold what styles the element will have at certain times.

The @keyframes Rule

When you specify CSS styles inside the @keyframes rule, the animation will gradually change from the current style to the new style at certain times. To get an animation to work, you must bind the animation to an element. The following example binds the "example" animation to the <div> element. The animation will last for 4 seconds, and it will gradually change the background-color of the <div>s element from "red" to "yellow":

Example 1: Using CSS animations part 1

/* The animation code */
@keyframes example {
  from {background-color: red;}
  to {background-color: yellow;}
}

/* The element to apply the animation to */
div {
  width: 100px;
  height: 100px;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
}

Note: The animation-duration property defines how long time an animation should take to complete. If the animation-duration property is not specified, no animation will occur, because the default value is 0s (0 seconds).

In the example above we have specified when the style will change by using the keywords "from" and "to" (which represents 0% (start) and 100% (complete)). It is also possible to use percent. By using percent, you can add as many style changes as you like. The following example will change the background-color of the <div> element when the animation is 25% complete, 50% complete, and again when the animation is 100% complete:

Example 2: Using CSS animations part 2

/* The animation code */
@keyframes example {
  0%   {background-color: red;}
  25%  {background-color: yellow;}
  50%  {background-color: blue;}
  100% {background-color: green;}
}

/* The element to apply the animation to */
div {
  width: 100px;
  height: 100px;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
}

The following example will change both the background-color and the position of the <div> element when the animation is 25% complete, 50% complete, and again when the animation is 100% complete:

Example 3: Using CSS animations part 3

/* The animation code */
@keyframes example {
  0%   {background-color:red; left:0px; top:0px;}
  25%  {background-color:yellow; left:200px; top:0px;}
  50%  {background-color:blue; left:200px; top:200px;}
  75%  {background-color:green; left:0px; top:200px;}
  100% {background-color:red; left:0px; top:0px;}
}

/* The element to apply the animation to */
div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
}

Delay an Animation

The animation-delay property specifies a delay for the start of an animation. The following example has a 2 seconds delay before starting the animation:

Example 4: Using the animation-delay property part 1

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-delay: 2s;
}

Negative values are also allowed. If using negative values, the animation will start as if it had already been playing for N seconds. In the following example, the animation will start as if it had already been playing for 2 seconds:

Example 5: Using the animation-delay property part 2

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-delay: -2s;
}

Set How Many Times an Animation Should Run

The animation-iteration-count property specifies the number of times an animation should run. The following example will run the animation 3 times before it stops:

Example 6: Using the animation-iteration-count property part 1

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-iteration-count: 3;
}

The following example uses the value "infinite" to make the animation continue for ever:

Example 7: Using the animation-iteration-count property part 2

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-iteration-count: infinite;
}

Run Animation in Reverse Direction or Alternate Cycles

The animation-direction property specifies whether an animation should be played forwards, backwards or in alternate cycles. The animation-direction property can have the following values:

• normal - The animation is played as normal (forwards). This is default
• reverse - The animation is played in reverse direction (backwards)
• alternate - The animation is played forwards first, then backwards
• alternate-reverse - The animation is played backwards first, then forwards

The following example will run the animation in reverse direction (backwards):

Example 8: Using the animation-direction property part 1

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-direction: reverse;
}

The following example uses the value "alternate" to make the animation run forwards first, then backwards:

Example 9: Using the animation-direction property part 2

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-iteration-count: 2;
  animation-direction: alternate;
}

The following example uses the value "alternate-reverse" to make the animation run backwards first, then forwards:

Example 10: Using the animation-direction property part 3

div {
  width: 100px;
  height: 100px;
  position: relative;
  background-color: red;
  animation-name: example;
  animation-duration: 4s;
  animation-iteration-count: 2;
  animation-direction: alternate-reverse;
}

Specify the Speed Curve of the Animation

The animation-timing-function property specifies the speed curve of the animation. The animation-timing-function property can have the following values:

• ease - Specifies an animation with a slow start, then fast, then end slowly (this is default)
• linear - Specifies an animation with the same speed from start to end
• ease-in - Specifies an animation with a slow start
• ease-out - Specifies an animation with a slow end
• ease-in-out - Specifies an animation with a slow start and end
• cubic-bezier(n,n,n,n) - Lets you define your own values in a cubic-bezier function

The following example shows the some of the different speed curves that can be used:

Example 11: Using the animation-timing-function property

#div1 {animation-timing-function: linear;}
#div2 {animation-timing-function: ease;}
#div3 {animation-timing-function: ease-in;}
#div4 {animation-timing-function: ease-out;}
#div5 {animation-timing-function: ease-in-out;}

Specify the fill-mode For an Animation

CSS animations do not affect an element before the first keyframe is played or after the last keyframe is played. The animation-fill-mode property can override this behavior.

The animation-fill-mode property specifies a style for the target element when the animation is not playing (before it starts, after it ends, or both). The animation-fill-mode property can have the following values:

• none - Default value. Animation will not apply any styles to the element before or after it is executing
• forwards - The element will retain the style values that is set by the last keyframe (depends on animation-direction and animation-iteration-count)
• backwards - The element will get the style values that is set by the first keyframe (depends on animation-direction), and retain this during the animation-delay period
• both - The animation will follow the rules for both forwards and backwards, extending the animation properties in both directions

The following example lets the <div> element retain the style values from the last keyframe when the animation ends:

Example 12: Using the animation-fill-mode property part 1

div {
  width: 100px;
  height: 100px;
  background: red;
  position: relative;
  animation-name: example;
  animation-duration: 3s;
  animation-fill-mode: forwards;
}

The following example lets the <div> element get the style values set by the first keyframe before the animation starts (during the animation-delay period):

Example 13: Using the animation-fill-mode property part 2

div {
  width: 100px;
  height: 100px;
  background: red;
  position: relative;
  animation-name: example;
  animation-duration: 3s;
  animation-delay: 2s;
  animation-fill-mode: backwards;
}

The following example lets the <div> element get the style values set by the first keyframe before the animation starts, and retain the style values from the last keyframe when the animation ends:

Example 14: Using the animation-fill-mode property part 3

div {
  width: 100px;
  height: 100px;
  background: red;
  position: relative;
  animation-name: example;
  animation-duration: 3s;
  animation-delay: 2s;
  animation-fill-mode: both;
}

Animation Shorthand Property

The example below uses six of the animation properties:

Example 14: Use six of the animation properties

div {
  animation-name: example;
  animation-duration: 5s;
  animation-timing-function: linear;
  animation-delay: 2s;
  animation-iteration-count: infinite;
  animation-direction: alternate;
}

The same animation effect as above can be achieved by using the shorthand animation property:

Example 15: Use the shorthand animation property

div {
  animation: example 5s linear 2s infinite alternate;
}

CSS Animation Properties

The following table lists the @keyframes rule and all the CSS animation properties:

Property	Description
@keyframes	Specifies the animation code
animation	A shorthand property for setting all the animation properties
animation-delay	Specifies a delay for the start of an animation
animation-direction	Specifies whether an animation should be played forwards, backwards or in alternate cycles
animation-duration	Specifies how long time an animation should take to complete one cycle
animation-fill-mode	Specifies a style for the element when the animation is not playing (before it starts, after it ends, or both)
animation-iteration-count	Specifies the number of times an animation should be played
animation-name	Specifies the name of the @keyframes animation
animation-play-state	Specifies whether the animation is running or paused
animation-timing-function	Specifies the speed curve of the animation