Friday, June 24, 2011

Few words about my CSS Nyan Cat

Last week Mozilla together with Finnish demoscene hackers organized Flame Party in capital of Finland, Helsinki. More than 100 participants worked whole day on outstanding web demos in two main categories - Single Effect and Main Demo.
Because of nearly release of stable Firefox 5, first Mozilla's browser with CSS3 Animation support, I decide to create CSS3 demo for the Single Effect Compo.
Since I really enjoy all that 4chan-like mems stuff, I chose Nyan Cat, as one of the most 'fresh' ones. In case you don't know it (check the progress bar!):

I didn't use any graphics to code my CSS Nyan Cat. It is completely drawn and animated in CSS. The 'pop-tart' body is created with two rounded cornered divs and big, pink dots separated with non-breaking spaces:
#toastBody {
    height: 70px;
    border: solid #000 5px;
    border-radius: 15px;
    padding: 2px;

#toastBody > div {
    border-radius: 30px;
    background-color: #fc9dff;
    color: #da3eb9;
    font-size: 40px;
    line-height: 10px;
All the animations was declared with @-moz/webkit-keyframe (I wrote a lot about this method before).

I made couple of unusual things during development. For example, look on the cat's mouth:

Yup, it is rotated 'E' letter:
<div id="mainHead" class="skin">
    <div class="mouth">E</div>

.mouth {
    position: absolute;
    -moz-transform: scale(2, 0.7) rotate(-90deg);
    -webkit-transform: scale(2, 0.7) rotate(-90deg);
    font-family: Arial;
    font-size: 25px;
    font-weight: bold;
    color: #000;

What about the rainbow behind the cat? I just cropped part of original image, put it into CSS Gradient Editor by ColorZilla (awesome tool BTW, but still without couple of necessary features I use daily; I think I will create something like this on my own), which generates me css gradient ready for pasting into the div background:
.rainbow {
 background: -moz-linear-gradient (top, #d91a12 15%, #e13300 15%, #ff7f14 16%, #f2ab03 32%, #ebc000 32%, #fade00 33%, #efff03 48%, #56fc02 49%, #52ff01 66%, #4ade7e 67%, #3baaf2 67%, #3baaf2 84%, #7337f7 84%, #6b40f2 100%);
The most annoying thing was the star. Animated stars in the background are made up from 8 animated elements. I google "nyan cat sprite" and found all the star frames [like this]. The only way to animate it was pixel-perfect animation of each of 8 divs. It took me really lot of time:
@-moz-keyframes star1 {
 0% { top: 0; height: 5px;}
 33.19% { top: 0; height: 5px; }
 33.2% { height:10px; top:0; }
 49.79% { height:10px; top:0; }
 49.8% { height:10px; top:5px; }
 66.39% {height:10px; top:5px; }
 66.4% { height:5px; top:10px;}
 82.99% { height:5px; top:10px;}
 83% { height: 5px; top: 15px; }
 99.99% { height: 5px; top: 15px; }
 100% { top: 0; height: 5px; }

@-moz-keyframes star2-3-6-7 {
 0% { visibility: hidden; }
 16.59% { visibility: hidden; }
 16.6% { visibility: visible; }
 33.19% { visibility: visible; }
 33.2% { visibility: hidden; }
 100% { visibility: hidden; }

@-moz-keyframes star4 {
 0% { left: 0; width: 5px; visibility: visible;}
 33.19% { left: 0; width: 5px; }
 33.2% { width:10px; left:0; }
 49.79% { width:10px; left:0; }
 49.8% { width:10px; left:5px; }
 66.39% {width:10px; left:5px; }
 66.4% { width:5px; left:10px;}
 82.99% { width:5px; left:10px;}
 83% { width: 5px; left: 15px; visibility:hidden;}
 99.99% { width: 5px; left: 15px; visibility:hidden;}
 100% { left: 0; width: 5px; visibility:hidden;}

@-moz-keyframes star5 {
 0% { left: 38px; width: 5px; visibility: visible;}
 33.19% { left: 38px; width: 5px; }
 33.2% { width:10px; left:33px; }
 49.79% { width:10px; left:33px; }
 49.8% { width:10px; left:28px; }
 66.39% {width:10px; left:28px; }
 66.4% { width:5px; left:28px;}
 82.99% { width:5px; left:28px;}
 83% { width: 5px; left: 15px; visibility:hidden;}
 99.99% { width: 5px; left: 15px; visibility:hidden;}
 100% { left: 0; width: 5px; visibility:hidden;}

@-moz-keyframes star8 {
 0% { top: 32px; height: 5px; visibility:visible;}
 33.19% { top: 32px; height: 5px; }
 33.2% { height:10px; top:28px; }
 49.79% { height:10px; top:28px; }
 49.8% { height:10px; top:23px; }
 66.39% {height:10px; top:23px; }
 66.4% { height:5px; top:18px;}
 82.99% { height:5px; top:18px;}
 83% { height: 5px; top: 15px; visibility:hidden;}
 99.99% { height: 5px; top: 15px; visibility:hidden;}
 100% { top: 0; height: 5px; visibility:hidden;}

.star {
 position: absolute;
 width: 40px;
 height: 40px;
 z-index: 10;

.star div {
 width: 5px;
 height: 5px;
 background-color: #fff;
 position: absolute;
 -moz-animation: star1 0.4s linear 0s infinite;
 -webkit-animation: star1 0.4s linear 0s infinite;

Here is the final result of everything: CSS NYAN CAT, and Github repo. If you like it, don't forget to click "I like it" on Mozilla's page!


  1. Lol, rotated E mouth rox!

  2. why rotated E instead of rotated 3?

  3. Coz it looks like 'E' in the original one.

  4. It's cute, but your audio loop needs work. It jumps rather noticeably -- or rather, it repeats the same fraction of a second, twice.

  5. yes
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    that is better for bigners for understanding.

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