Mobile is a tough nut to crack, due to some hard constraints on the CPU&#x2F;power consumption, but it&#x27;s getting better.  A new iPhone 5s does a pretty good job with something like that app I linked to, whereas an older Samsung Galaxy Tab 2 does not.  A lot also depends upon the browser, since there is a <i>big</i> difference between the JS engines in Chrome (best, by far) and FF&#x2F;IE when it comes to things like requestAnimationFrame() execution performance.  The linked-to example is a dog when run on IE 11&#x2F;Windows 8 on a practically-new Dell laptop&#x2F;tablet convertible with an i3, but works nicely in Chrome on the same device.<p>Re: CSS grids - totally agree.  But, what I&#x27;ve learned over the last 4 years of developing a web application IDE is this: CSS is great if you want to set the layout and leave it alone (for the most part).  In other words, when the JS is decorative, things are great.  When the JS becomes the primary actor, things start to break down due to lack of control over how&#x2F;when the reflows&#x2F;repaints occur.