How to use pure css to animate an hourglass

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Https://github.com/comehope/front-end-daily-challenges

Code interpretation

Defines the DOM, which contains 2 elements, representing the top and bottom halves of the hourglass, respectively:

<div class= "Loader" >    <span class= "Top" ></span>    <span class= "Bottom" ></span> </div>

Center display:

body {    margin:0;    HEIGHT:100VH;    Display:flex;    Align-items:center;    Justify-content:center;    Background-color:gainsboro;}

Define the container dimensions and set the overall layout of the child elements:

. loader {    width:4.3em;    Height:9.8em;    font-size:10px;    position:relative;    Display:flex;    Flex-direction:column;    Align-items:center;    Justify-content:space-between;}

Draw a square of 2 squares:

. top,.bottom {    width:3.5em;    height:3.5em;    Border-style:solid;    Border-color:saddlebrown;}

Turn 2 squares into hourglass shapes with borders, fillets, and rotations:

. top,.bottom {    border-width:0.2em 0.2em 0.6em 0.6em;    border-radius:50% 100% 50% 30%;}. Top {    transform:rotate ( -45deg);}. Bottom {    transform:rotate (135deg);}

The sand is painted with pseudo-elements, the top of the upper sand is a large arc, and the lower part of the sand is a small arc:

. top::before,.bottom::before {    content: ';    Position:absolute;    Width:inherit;    Height:inherit;    Background-color:deepskyblue;}. Top::before {    border-radius:0 100% 0 0;}. Bottom::before {    border-radius:0 0 0 35%;}

Define animation properties for sand:

. top::before,.bottom::before {    animation:2s linear infinite;}

Increase the animation effect of sand falling from the top half of the hourglass:

. top::before {    Animation-name:drop-sand;} @keyframes Drop-sand {    to {        transform:translate ( -2.5em, 2.5em);    }}

An animated effect that increases the sand's hourglass in the lower half:

. bottom::before {    transform:translate (2.5em, -2.5em);    Animation-name:fill-sand;} @keyframes Fill-sand {    to {        transform:translate (0, 0);}    }

Hide the upper half of the hourglass and the lower part of the container, at which point the top 2 animations overlay The sand from the top half and slowly accumulate in the lower half:

. top,.bottom {    Overflow:hidden;}

Create a narrow strip with the pseudo elements of the outer container to simulate the flowing sand:

. loader::after {    content: ';    Position:absolute;    Width:0.2em;    Height:4.8em;    Background-color:deepskyblue;    Top:1em;}

Animated effect of increasing sand flow:

. loader::after {    animation:flow 2s linear infinite;} @keyframes Flow {    10%, 100% {        transform:translatey (3.2EM);    }}

Finally, increase the rollover animation for the Hourglass:

. loader {    animation:rotating 2s linear infinite;} @keyframes Rotating {    0, 90% {        transform:rotate (0);    }        100% {        transform:rotate (0.5turn);    }}

Done!