CSS animations allows elements on a page to change their styles in specified order and duration. This is different from transition which makes smooth changes on a property. With animations, you manually set up the animation style of the properties of the element at different point in time. These animations do not require Javascript. It's pure CSS.

Syntax

CSS animations can be made up of two parts: The CSS style declaration for the animiation and a set of keyframes which specifies different points in time which styles are applied. Example:

element {
  animation-name: spin;
  animation-duration: 2s;
}
@keyframes animation {
  0% {
    transform: rotate(40deg);
  }
  100% {
    transform: rotate(100deg);
  }
}

In the above, the animation name spin is declared for the element. This speicification would act on any keyframe with the same name. The keyframes specify several points in time whereby the properties and values would be changed.

At the keyframes section, it is specified that at 0% of 2 seconds, the element would rotate by 40deg and at 100% of 2 seconds, the element would rotate by 100deg.

Another easier configuration for the above is:

@keyframes animation {
  from {
    transform: rotate(40deg);
  }
  to {
    transform: rotate(100deg);
  }
}

from is the same thing as 0% and to refers to 100%. For 2 seconds, CSS would determine the rotation at every point in time from % to 100%.

To manually calculate this, we have 100deg - 40deg = 60deg being the difference in degrees. 60/100 = 0.6 been the degree per percentage. So at 0% of 2 seconds, the element has a rotation degree of 40, at 1%, the rotation degree becomes 40.6 and so on until 100%.

Time points between 0% and 100% can also be specified with different styles. An example is:

@keyframes animation {
  from {
    transform: rotate(40deg);
  }
  45% {
    transform: rotate(80deg);
  }
  to {
    transform: rotate(100deg);
  }
}

CSS does the calculations for us to determine how fast the animation should be from 0% to 45% and from 45% to 100%.

Animation sub-properties

There's more to animation-name and animation-duration which are the required properties. More sub-properties of animation which are optional are:

• animation-delay: Specifies the time which the elements is placed on the page and the time which the animation begins. e.g 200ms

• animation-iteration-count: Specifies the number of times which the animation would repeat.

  • 1,2,3 to n value states the number of animation iterations.
  • infinite value means the animation would continue non-stop.

• animation-direction: Specifies how the animation should be directed (if the animation is run more than once). i.e At the end, should it start from the beginning, or it should it animate from the last keyframe back to the first keyframe.

  • reverse value means the animation would go from 100% to 0% always.
  • alternate value means the animation would go from 0% to 100% and from 100% to 0%,

• animation-timing-function: Specifies how an animation is timed. This creates animation curves and can be used for smooth animations.

  • linear value means the normal animation as specified in the keyframes.
  • ease value means the animation executes in ease mode. Not fast mode.
  • ease-in value means the animation begins in ease mode, more of like a slow entry before a fast execution.
  • ease-in-out value means the animation begins in ease mode, executes fast, then ends in ease mode. More of like, slow entry, slow exit.

• animation-fill-mode: Specifies the values that the animation applies before and after it is activated.

  • backwards value means that the element will possess the style declared in the first keyframe before the animation begins. You can practilize this by setting an animation-delay to be greater than 0 seconds.
  • forwards value means the element will possess the style declared in the last keyframe after the animation ends.
  • both value means backwards and forwards apply.

• animation-play-state: This is used in pausing or playing an animation sequence.

  • running which is the default value specifies that the animation is running.
  • pause value means the animation would be paused.

Shorthand animation style declareation

CSS has an easier way of specifying animation style.

Instead of specifying all sub-properties, you can use a short-hand property called animation. An example is:

element {
  animation: spin 2s infinite alternate 3s backwards;
}

In the above, we can see that:

• spin: animation-name
• 2s: animation duration
• infinite: animation-iteration-count
• alternate: animation-direction
• 3s: animation-delay
• backwards: animation-fill-mode

are all stated as values for the animation property.

Order of specifying animation

There is no formal way of specifying the values in the animation property. The value must begin with the animation-name then all other sub-properties can follow.

Almost all sub-properties have different values thereby making it easy for CSS to determine which value is for which property.

However, animation-delay and animation-duration have the same values - time (in seconds and milliseconds). For this reason, the rule is that animation-duration must come before animation-delay.

Use of multiple animations

Multiple animations can be specified for elements. An example is:

element {
  animation-name: spin, moveRight;
  animation-delay: 2s;
  animation-duration: 3s 5s;
  animation-iteration-count: infinite 4;
}
@keyframes spin {
  from {
    transform: rotate(40deg);
  }
  to {
    transform: rotate(100deg);
  }
}
@keyframes moveRight {
  from {
    margin-left: 20px;
  }
  to {
    margin-left: 100px;
  }
}

The above specifies two animations for the element which are spin and moveRight. It has a single value in animation-delay of 2s. This applies to both animations. It has two values for animation-duration which are 3s and 5s. 3s is used for spin and 5s is used for moveRight. The last sub-property declared is animation-iteration-count which has two values: infinite for spin and 4 for moveRight.

The shorthand representation of the above is:

element {
  animation: spin 3s 2s infinite, moveRight 5s 2s 4;
}

Thanks for reading 💛