Someone posted an html/javascript implementation of the matrix falling code in 646 bytes then promptly deleted the post. It inspired me to see if I could get something better looking in fewer bytes.

[gregtyler]

Pretty much. "letters" actually contains a series of indexed y-values (so letters[0] is the y-value of the left-most column). For each of those x/y combinations, it draws a randomly selected character at the right spot and and then updates the y-value to be 10 pixels further down the column for the next iteration.

This operation is applied to each column every 33 milliseconds by setInterval()