csswg-drafts/css3-animations/Overview.src.html at b95186541e2be5d52520dfa09959eb3baf598d5f · w3c/csswg-drafts · GitHub

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<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
  'http://www.w3.org/TR/html4/strict.dtd'>

<html lang="en">
<head>
  <title>CSS Animations</title>
  <link rel="stylesheet" type="text/css" href="default.css">
  <style type="text/css">
    .rhs { white-space: pre-wrap; }
    code { font-size: inherit; }
    #box-shadow-samples td { background: white; color: black; }

    table {
      border-collapse: collapse;
    }
    td {
      padding: 0.2em 1em;
      border: 1px solid black;
    }
  </style>
  <link rel="stylesheet" type="text/css"
  href="http://www.w3.org/StyleSheets/TR/W3C-WD.css">
</head>

<body>

<div class="head">
<!--logo-->

<h1>CSS Animations</h1>

<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
  <dt>This version:
    <dd><a href="[VERSION]">http://dev.w3.org/csswg/css3-animations/</a>
    <!--http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]-->
  <dt>Latest version:
    <dd><a
      href="http://www.w3.org/TR/css3-animations">[LATEST]</a>
  <dt>Previous version:
    <dd><a href="http://www.w3.org/TR/2009/WD-css3-animations-20090320/">
      http://www.w3.org/TR/2009/WD-css3-animations-20090320/</a>
  <dt id="editors-list">Editors:
    <dd><a href="mailto:dino@apple.com">Dean Jackson</a> (<a
      href="http://www.apple.com/">Apple Inc</a>)
    <dd><a href="mailto:hyatt@apple.com">David Hyatt</a> (<a
      href="http://www.apple.com/">Apple Inc</a>)
    <dd><a href="mailto:cmarrin@apple.com">Chris Marrin</a> (<a
      href="http://www.apple.com/">Apple Inc</a>)
</dl>

<!--copyright-->

<hr title="Separator for header">
</div>

<h2 class="no-num no-toc" id="abstract">Abstract</h2>

<p>This CSS module describes a way for authors to animate the values of CSS properties over time, using keyframes.
    The behavior of these keyframe animations can be controlled by specifying their duration, number of repeats,
    and repeating behavior.
</p>

<h2 class="no-num no-toc" id="status">Status of this document</h2>
<!--status-->


<h2 class="no-num no-toc" id="contents">Table of contents</h2>
<!--toc-->


<h2 id="introduction">Introduction</h2>

    <p><em>This section is not normative.</em>

    <p>
        CSS Transitions [[!CSS3-TRANSITIONS]] provide a way to interpolate CSS property values
        when they change as a result of underlying property changes. This provides an easy way to do simple animation,
        but the start and end states of the animation are controlled by the existing property values,
        and transitions provide little control to the author on how the animation progresses.
    </p>
    <p>
        This proposal introduces <em>defined animations</em>, in which the author can
        specify the changes in CSS properties over time as a set of keyframes. Animations are similar to transitions
        in that they change the presentational value of CSS properties over time.
        The principal difference is that while transitions trigger <i>implicitly</i> when property values change, animations
        are <i>explicitly</i> executed when the animation properties are applied. Because of this, animations require explicit
        values for the properties being animated. These values are specified using animation keyframes, described below.
    </p>
    <p>
        Many aspects of the animation can be controlled, including how many times the animation iterates, whether or not
        it alternates between the begin and end values, and whether or not the animation should be running or paused.
        An animation can also delay its start time.
    </p>

    <h2>Animations</h2>

    <p>
      CSS Animations affect computed property values. During the execution of an animation, the
      computed value for a property is controlled by the animation. This overrides the value
      specified in the normal styling system.
    </p>

    <p>
      In the case of multiple animations specifying behavior for the same property, the animation
      defined last will override the previously defined animations.
    </p>

    <p>
      An animation does not affect the computed value before the application of the animation,
      before the animation delay has expired, and after the end of the animation.
    </p>

    <div class="figure">
      <img src="sandwich.png" alt="">
    </div>
    <p class="caption">
      Computation of animated property values
    </p>

    <p>
      The diagram above shows how property values are computed. The intrinsic style is shown at the
      top of the diagram. The computed value is derived from intrinsic style at the times when an
      animation is not running and also when an animation is delayed (see below for specification of
      animation delay). During an animation, the computed style is derived from the animated value.
    </p>

    <p>
      The start time of an animation is the latter of two moments: the time at which the style is
      resolved that specifies the animation, or the time the document's load event is fired.
      Therefore, an animation specified in the document stylesheet will begin at the document load.
      An animation specified on an element by modifying the style after the document has loaded will
      start when the style is resolved. That may be immediately in the case of a pseudo style rule
      such as hover, or may be when the scripting engine returns control to the browser (in the case
      of style applied by script).
    </p>

    <p>
      An animation applies to an element if the element has a value for
      <span class="prop-name">'animation-name'</span> that references a valid
      keyframes rule. Once an animation has started it continues until it ends
      or the <span class="prop-name">'animation-name'</span> is removed. The values
      used for the keyframes and animation properties are snapshotted at the
      time the animation starts. Changing them during the execution of the
      animation has no effect. Note also, that changing the value of
      <span class="prop-name">'animation-name'</span> does not necessarily
      restart an animation (e.g. if a list of animations are applied and
      one is removed from the list, only that animation will stop; The other
      animations will continue). In order to restart an animation, it must be
      removed then reapplied.
    </p>

    <p>
      The end of the animation is defined by the combination of the
      <span class="prop-name">'animation-duration'</span>,
      <span class="prop-name">'animation-iteration-count'</span> and
      <span class="prop-name">'animation-fill-mode'</span> properties.
    </p>

    <div class="example">
      <p style="display:none">
        Example(s):
      </p>
      <pre>
    div {
      animation-name: diagonal-slide;
      animation-duration: 5s;
      animation-iteration-count: 10;
    }

    @keyframes diagonal-slide {

      from {
        left: 0;
        top: 0;
      }

      to {
        left: 100px;
        top: 100px;
      }

    }

    </pre>This will produce an animation that moves an element from (0, 0) to (100px, 100px) over five seconds and repeats itself nine times (for a total of ten iterations).
    </div>

    <h2>Keyframes</h2>
      <p>
        Keyframes are used to specify the values for the animating properties at various points
        during the animation. The keyframes specify the behavior of one cycle of the animation;
        the animation may iterate one or more times.
      </p>
      <p>
        Keyframes are specified using a specialized CSS at-rule. A <span
        class="prop-name">@keyframes</span> rule consists of the keyword
        "@keyframes", followed by an identifier giving a name for the animation
        (which will be referenced using <span
        class="prop-name">'animation-name'</span>), followed by a set of style
        rules (delimited by curly braces).
      </p>
      <p>
        The <i>keyframe selector</i> for a keyframe style rule consists of a
        comma-separated list of percentage values or the keywords 'from' or
        'to'. The selector is used to specify the percentage along the duration
        of the animation that the keyframe represents. The
        keyframe itself is specified by the block of property values declared on
        the selector. The keyword 'from' is equivalent to the value 0%. The
        keyword 'to' is equivalent to the value 100%. Note that the percentage
        unit specifier must be used on percentage values. Therefore, "0" is an
        invalid keyframe selector.
      </p>
      <p>
        If a 0% or "from" keyframe is not specified, then the user agent
        constructs a 0% keyframe using the computed values of the properties
        being animated. If a 100% or "to" keyframe is not specified, then the user agent
        constructs a 100% keyframe using the computed values of the properties
        being animated.
      </p>
      <p>
        The <i>keyframe declaration</i> for a keyframe rule consists of
        properties and values. Properties that are unable to be
        animated are ignored in these rules, with the exception of <span
        class="prop-name">animation-timing-function'</span>, the behavior
        of which is described below.
      </p>
      <p class="note">
          NOTE: describe what happens if a property is not present in all keyframes.
      </p>
      <p>
        The @keyframes rule that is used by an animation will be the last one encountered in sorted rules order
        that matches the name of the animation specified by the <span class="prop-name">'animation-name'</span> property.
        <span class="prop-name">@keyframes</span> rules do not cascade;
        therefore an animation will never derive keyframes from more than one <span class="prop-name">@keyframes</span> rule.
      </p>
      <p>
        To determine the set of keyframes, all of the values in selectors are sorted in increasing order by time.
        If there are any duplicates, then the last keyframe specified inside the <span class="prop-name">@keyframes</span> rule
        will be used to provide the keyframe information for that time. There is no cascading within a
        <span class="prop-name">@keyframes</span> rule if multiple keyframes specify the same keyframe selector values.
      </p>
      <div class="example">
        <p style="display:none">
          Example(s):
        </p>
        <pre>
  @keyframes wobble {

    0% {
      left: 100px;
    }

    40% {
      left: 150px;
    }

    60% {
      left: 75px;
    }

    100% {
      left: 100px;
    }

  }

  </pre>Four keyframes are specified for the animation named "wobble". In the first keyframe, shown at the beginning of the animation cycle, the 'left' value of the animation is 100px. By 40% of the animation duration, 'left' value has animated to 150px. At 60% of the animation duration, the 'left' value has animated back to 75px. At the end of the animation cycle, the 'left' value has returned to 100px. The diagram below shows the state of the animation if it were given a duration of 10s.
        <div class="figure">
          <img src="animation1.png" alt="">
        </div>
        <p class="caption">
          Animations states specified by keyframes
        </p>
      </div>

      <p>
        The following is the grammar for the keyframes rule.
      </p>

      <pre>
        keyframes-rule: '@keyframes' IDENT '{' keyframes-blocks '}';

        keyframes-blocks: [ keyframe-selectors block ]* ;

        keyframe-selectors: [ 'from' | 'to' | PERCENTAGE ] [ ',' [ 'from' | 'to' | PERCENTAGE ] ]*;
      </pre>
      <!-- ======================================================================================================= -->
      <h3>
        Timing functions for keyframes
      </h3>
      <p>
        A keyframe style rule may also declare the timing function that is to be used as the animation moves to the next keyframe.
      </p>
      <div class="example">
        <p style="display:none">
          Example(s):
        </p>
        <pre>
  @keyframes bounce {

    from {
      top: 100px;
      animation-timing-function: ease-out;
    }

    25% {
      top: 50px;
      animation-timing-function: ease-in;
    }

    50% {
      top: 100px;
      animation-timing-function: ease-out;
    }

    75% {
      top: 75px;
      animation-timing-function: ease-in;
    }

    to {
      top: 100px;
    }

  }

  </pre>Five keyframes are specified for the animation named "bounce". Between the first and second keyframe (ie. between 0 and 25%) an "ease-out" timing function is used. Between the second and third keyframe (ie. between 25% and 50%) an "ease-in" timing function is used. And so on. The effect will appear as an element that moves up the page 50px, slowing down as it reaches its highest point then speeding up as it falls back to 100px. The second half of the animation behaves in a similar manner, but only moves the element 25px units up the page. A timing function specified on the "to" or 100% keyframe is ignored
      </div>
      <p>
        See <a href="#animation-timing-function_tag">the <span class="prop-name">'animation-timing-function'</span> property</a> for more information.
      </p><!-- ======================================================================================================= -->

      <!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-name'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-name'</span> property defines a
        list of animations that apply. Each name is used to select the keyframe at-rule
        that provides the property values for the animation. If the name does
        not match any keyframe at-rule, there are no properties to be animated
        and the animation will not execute. Furthermore, if the animation name
        is 'none' then there will be no animation. This can be used to override
        any animations coming from the cascade. If animations are attempting to
        modify the same property, then the animation closest to the end of the
        list of names wins.
      </p>
      <p>
        Each animation listed by name should have a corresponding value
        for the other animation properties listed below. In the case where the
        other properties do not have lists of the correct length, their values
        are repeated to form a list with the same number of entries as
        <span class="prop-name">'animation-name'</span>.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-name">animation-name</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              none | IDENT [, none | IDENT ]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              none
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table>

      <!--
      <p>
        It is possible for elements to have multiple animations running that change the same property or properties. In this case the animations combine in a manner defined by the property. For example, animations on <span class="prop-name">opacity</span> will add together and animations on <span class="prop-name">transform</span> will have their transformation matrices multiplied.
      </p>
      <div class="example">
        <p style="display:none">
          Example(s):
        </p>
        <pre>
        @keyframes 'border-bloat' {
          from {
            border-width: 0;
          }
          to {
            border-width: 10px;
          }
        }

        @keyframes 'border-diet' {
          from {
            border-width: 4px;
          }
          to {
            border-width: 2px;
          }
        }

        div {
          animation-name: 'border-bloat', 'border-diet';
          animation-duration: 10s, 4s;
        }
      </pre>
      <p>
      The above example has two animations executing on the same property, <span class="prop-name">border-width</span>. The animations are additive. That is, the
      resulting value for the property will be the addition of the values from the
      two animations.
      </p>
      <p>
        At time '0s' the element's border will be 4px wide (0px from 'border-bloat' plus 4px from 'border-diet').
        At time '4s' the element's border will be 6px wide (4px from 'border-bloat' plus 2px from 'border-diet').
        At time '10s' the element's border will be 10px wide (10px from 'border-bloat' and no addition from
        'border-diet' as it is no longer executing).
      </p>
    </div>
  -->


      <!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-duration'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-duration'</span> property defines the length of time that an animation takes to complete one cycle.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-duration">animation-duration</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              &lt;time&gt; [, &lt;time&gt;]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              0
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table>

      <p>
        By default the value is '0', meaning that the animation cycle is
        immediate. A negative value for <span
        class="prop-name">animation-duration</span> is treated as '0'. In this
        case <span class="prop-name">animation-fill-mode</span> still applies,
        so an animation that fills backwards will show the value of the 0%
        keyframe during any delay period, and an animation that fill forwards
        will retain the value specified at the 100% keyframe, even if the
        animation was instantaneous. Also, animation events are still fired.
      </p>

      <!-- ======================================================================================================= -->
      <h3 id="animation-timing-function_tag">
        The <span class="prop-name">'animation-timing-function'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-timing-function'</span> property describes how the animation will progress over one cycle of its duration. See the <span class="prop-name">'transition-timing-function'</span> property [[!CSS3-TRANSITIONS]] for a complete description of timing function calculation.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-timing-function">animation-timing-function</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(&lt;number&gt;[, start | end ]) | cubic-bezier(&lt;number&gt;, &lt;number&gt;, &lt;number&gt;, &lt;number&gt;) [, ease | linear | ease-in | ease-out | ease-in-out | step-start | step-end | steps(&lt;number&gt;[, start | end ]) | cubic-bezier(&lt;number&gt;, &lt;number&gt;, &lt;num
ADFF
ber&gt;, &lt;number&gt;)]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              ease
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table>

      <p>
        For a keyframed animation, the <span class="prop-name">'animation-timing-function'</span> applies
        between keyframes, not over the entire animation. For example, in the case of an ease-in-out timing function, an animation will ease in at the start of the keyframe and ease out at the end of the keyframe. A <span class="prop-name">'animation-timing-function'</span> defined within a keyframe block applies to that keyframe, otherwise the timing function specified for the animation is used.
      </p>

      <!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-iteration-count'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-iteration-count'</span> property defines the number of times an animation cycle is played. The default value is one, meaning the animation will play from beginning to end once. A value of <span class="prop-value">'infinite'</span> will cause the animation to repeat forever. Non-integer numbers will cause the animation to end part-way through a cycle. Negative values for <span class="prop-name">'animation-iteration-count'</span> are treated as zero. This property is often used with an <span class="prop-name">'animation-direction'</span> value of <span class="prop-value">'alternate'</span>, which will cause the animation to play in reverse on alternate cycles.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-iteration-count">animation-iteration-count</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              infinite | &lt;number&gt; [, infinite | &lt;number&gt;]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              1
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table><!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-direction'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-direction'</span> property defines whether or not the animation should play in reverse on alternate cycles. If <span class="prop-value">'alternate'</span> is specified, the animation cycle iterations that are odd counts are played in the normal direction, and the animation cycle iterations that are even counts are played in a reverse direction. When an animation is played in reverse the timing functions are also reversed. For example, when played in reverse an ease-in animation would appear to be an ease-out animation.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-direction">animation-direction</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              normal | alternate [, normal | alternate]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              normal
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table><!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-play-state'</span> Property
      </h3>

      <p>
        The <span class="prop-name">'animation-play-state'</span> property defines whether the animation is running or paused. A running animation can be paused by setting this property to <span class="prop-value">'paused'</span>. To continue running a paused animation this property can be set to <span class="prop-value">'running'</span>. A paused animation will continue to display the current value of the animation in a static state, as if the time of the animation is constant. When a paused animation is resumed, it restarts from the current value, not necessarily from the beginning of the animation.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-play-state">animation-play-state</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              running | paused [, running | paused]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
              running
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table><!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-delay'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-delay'</span> property defines
        when the animation will start. It allows an animation to begin
        execution some time after it is applied. An <span
        class="prop-name">'animation-delay'</span> value of '0' means the
        animation will execute as soon as it is applied. Otherwise, the value
        specifies an offset from the moment the animation is applied, and the
        animation will delay execution by that offset.
      </p>
      <p>
        If the value for <span class="prop-name">'animation-delay'</span> is a
        negative time offset then the animation will execute the moment it is
        applied, but will appear to have begun execution at the specified
        offset. That is, the animation will appear to begin part-way through
        its play cycle. In the case where an animation has implied starting
        values and a negative <span
        class="prop-name">'animation-delay'</span>, the starting values are
        taken from the moment the animation is applied.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-delay">animation-delay</dfn>
            </td>
          </tr>
          <tr>
            <td>
              <em>Value:</em>
            </td>
            <td>
              &lt;time&gt; [, &lt;time&gt;]*
            </td>
          </tr>
          <tr>
            <td>
              <em>Initial:</em>
            </td>
            <td>
            </td>
          </tr>
          <tr>
            <td>
              <em>Applies&nbsp;to:</em>
            </td>
            <td>
              block-level and inline-level elements
            </td>
          </tr>
          <tr>
            <td>
              <em>Inherited:</em>
            </td>
            <td>
              no
            </td>
          </tr>
          <tr>
            <td>
              <em>Percentages:</em>
            </td>
            <td>
              N/A
            </td>
          </tr>
          <tr>
            <td>
              <em>Media:</em>
            </td>
            <td>
              visual
            </td>
          </tr>
          <tr>
            <td>
              <em>Computed value:</em>
            </td>
            <td>
              Same as specified value.
            </td>
          </tr>
        </tbody>
      </table><!-- ======================================================================================================= -->
      <h3>
        The <span class="prop-name">'animation-fill-mode'</span> Property
      </h3>
      <p>
        The <span class="prop-name">'animation-fill-mode'</span> property defines
        what values are applied by the animation outside the time it is executing.
        By default, an animation will not affect property values between the
        time it is applied (the <span class="prop-name">'animation-name'</span> property is
        set on an element) and the time it begins execution (which is determined by
        the <span class="prop-name">'animation-delay'</span> property). Also, by
        default an animation does not affect property values after the animation
        ends (determined by the <span class="prop-name">'animation-duration'</span> property).
        The value of <span class="prop-name">'animation-fill-mode'</span> can
        override this behavior.
      </p>
      <p>
        If the value for <span class="prop-name">'animation-fill-mode'</span> is
        <span class="prop-value">'backwards'</span>, then the animation will
        apply the property values defined in its 0% or 'from' keyframe as soon
        as the animation is applied, during the period defined by
        <span class="prop-name">'animation-delay'</span>.
      </p>
      <p>
        If the value for <span class="prop-name">'animation-fill-mode'</span>
        is <span class="prop-value">'forwards'</span>, then the animation will
        apply the property values defined in its last executing keyframe after
        the final iteration of the animation, until the animation style is
        removed. The last executing keyframe is the 'to' or '100%' keyframe,
        unless the animation has <span
        class="prop-name">'animation-direction'</span> set to <span
        class="prop-value">'alternate'</span> and both a finite and even
        iteration count, in which case it is the 'from' or '0%' keyframe.
      </p>
      <p>
        If the value for <span class="prop-name">'animation-fill-mode'</span>
        is <span class="prop-value">'both'</span>, then the animation will
        follow the rules for both 'forwards' and 'backwards'. That is, it will
        extend the animation properties in both directions.
      </p>
      <table class="propdef">
        <tbody>
          <tr>
            <td>
              <em>Name:</em>
            </td>
            <td>
              <dfn id="animation-fill-mode">animation-fill-mode</dfn>
            </td>