offset-position

normal

Indicates that the element does not have an offset starting position and places the element at 50% 50% of the containing block. This is the default value.

auto

Indicates that the offset starting position is the top-left corner of the element's box.

<position>

Specifies the position as an x/y coordinate to place an element relative to its box edges. The position can be defined using one to four values. If two non-keyword values are used, the first value represents the horizontal position and the second represents the vertical position. If only one value is specified, the second value is assumed to be center. If three or four values are used, the <length-percentage> values are offsets for the preceding keyword value(s). For more explanation of these value types, see background-position.

offset-position = 
  normal      |
  auto        |
  <position>  

<position> = 
  [ left | center | right | top | bottom | <length-percentage> ]  |
  [ left | center | right ] && [ top | center | bottom ]  |
  [ left | center | right | <length-percentage> ] [ top | center | bottom | <length-percentage> ]  |
  [ [ left | right ] <length-percentage> ] && [ [ top | bottom ] <length-percentage> ]  

<length-percentage> = 
  <length>      |
  <percentage>  

In this example, the offset-path property is used to define the path along which the cyan element should move. The value of the path() CSS function is an SVG data path that describes a curved path. The element moves along this curved path during the move animation.

HTML

<div id="wrap">
  <div id="motion-demo"></div>
</div>

CSS

#motion-demo {
  offset-path: path("M20,20 C20,100 200,0 200,100");
  offset-position: left top;
  animation: move 3000ms infinite alternate ease-in-out;
  width: 40px;
  height: 40px;
  background: cyan;
}

@keyframes move {
  0%,
  20% {
    offset-distance: 0%;
  }
  80%,
  100% {
    offset-distance: 100%;
  }
}

Result

This example visually compares various initial offset starting position of an element when ray() is used to specify a value for the offset-path property. The number inside the element box indicates the element to which CSS is applied as well as the element's anchor point.

.box {
  background-color: green;
  border-top: 6px dashed white;
  background-clip: border-box;
  position: absolute;
  top: 20px;
  left: 20px;
  opacity: 20%;
  color: white;
}

.box0 {
  offset-position: normal;
}

.box1 {
  offset-position: normal;
  offset-path: ray(0deg);
}

.box2 {
  offset-position: auto;
  offset-path: ray(0deg);
}

.box3 {
  offset-position: left top;
  offset-path: ray(0deg);
}

.box4 {
  offset-position: 30% 70%;
  offset-path: ray(120deg);
}

Result

In box0, the absence of the offset-path property means that an offset-position of either normal or auto has no effect. When offset-position is normal, the ray starts at the center of the containing block (i.e., 50% 50%). This is the default starting position of an offset path and is used when no offset-position is specified. Notice the difference between offset starting positions auto and left top. The value auto aligns the element's anchor point to its own top-left corner, whereas the value left top aligns the element's anchor point to the top-left corner of the containing block.

• offset
• offset-anchor
• offset-distance
• offset-path
• offset-rotate