Revision 7027534b-9e18-4204-96fa-5ca013bc6c48

# HTML / JavaScript, 156

<!-- language: lang-html -->

    <body onload="t=c.getContext('2d');t[f='fillRect'](0,0,w=270,h=150);t.fillStyle='#07d';setInterval('n=Math.random()*4e4;t[f](n%w,n/h,1,1)',1)"><canvas id=c>

Testable version in [JSFiddle](http://jsfiddle.net/ooflorent/d26k7/).  
Preview:

![raindrop][1]

Annotated version:

<!-- language: lang-html -->

    <body>
    <canvas id="c"></canvas>
    <script>
      onload = function() {
        // Retrieve the rendering context
        t=c.getContext('2d');
        // Fill the canvas with black
        t[f='fillRect'](0,0,w=270,h=150);
        // Set rain color
        t.fillStyle='#07d';
        // Render whenever it is possible
        setInterval(function() {
          // Generate a number between 0 and 40,000
          // 40,000 ~= 270 * 150
          n=Math.random()*4e4;
          // Draw a raindrop.
          // Since x and y are not rounded, the raindrop looks blurry!
          t[f](n%w,n/h,1,1)
        }, 1);
      };
    </script>
    </body>


  [1]: https://i.sstatic.net/NCSz5.gif