Nice.

I just wasted 20 minutes messing with this in work trying to figure out what I could do.

If I hold a key down for 10 seconds or so the letters tend to rain down about a minute later lol.

Nice but needs some form of clean up running as the animation slows down more and more. A quick peak at the code shows there's a platform to catch the letter but there doesn't appear to be a clean up to delete them after?

That's right. I should delete the letters after they collide with the platform.

Nice.

Its performance in Chrome is very good. But in Safari it is very bad.

those words like matrix reload

Fantastic!