A Matrix-ish display for Bash terminal

matrixish.sh

#!/bin/bash
#
# matrix: matrix-ish display for Bash terminal
# Author: Brett Terpstra 2012 <http://brettterpstra.com>
# Contributors: Lauri Ranta and Carl <http://blog.carlsensei.com/>
#
# A morning project. Could have been better, but I'm learning when to stop.

### Customization:
blue="\033[0;34m"
brightblue="\033[1;34m"
cyan="\033[0;36m"
brightcyan="\033[1;36m"
green="\033[0;32m"
brightgreen="\033[1;32m"
red="\033[0;31m"
brightred="\033[1;31m"
white="\033[1;37m"
black="\033[0;30m"
grey="\033[0;37m"
darkgrey="\033[1;30m"
# Choose the colors that will be used from the above list
# space-separated list
# e.g. `colors=($green $brightgreen $darkgrey $white)`
colors=($green $brightgreen)
### End customization

### Do not edit below this line
spacing=${1:-100} # the likelihood of a character being left in place
scroll=${2:-0} # 0 for static, positive integer determines scroll speed
screenlines=$(expr `tput lines` - 1 + $scroll)
screencols=$(expr `tput cols` / 2 - 1)

# chars=(a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 0 1 2 3 4 5 6 7 8 9 ^)
# charset via Carl:
chars=(ｱ ｲ ｳ ｴ ｵ ｶ ｷ ｸ ｹ ｺ ｻ ｼ ｽ ｾ ｿ ﾀ ﾁ ﾂ ﾃ ﾄ ﾅ ﾆ ﾇ ﾈ ﾉ ﾊ ﾋ ﾌ ﾍ ﾎ ﾏ ﾐ ﾑ ﾒ ﾓ ﾔ ﾕ ﾖ ﾗ ﾘ ﾙ ﾚ ﾛ ﾜ ﾝ)

count=${#chars[@]}
colorcount=${#colors[@]}

trap "tput sgr0; clear; exit" SIGTERM SIGINT

if [[ $1 =~ '-h' ]]; then
	echo "Display a Matrix(ish) screen in the terminal"
	echo "Usage:		matrix [SPACING [SCROLL]]"
	echo "Example:	matrix 100 0"
	exit 0
fi


clear
tput cup 0 0
while :
	do for i in $(eval echo {1..$screenlines})
		do for i in $(eval echo {1..$screencols})
			do rand=$(($RANDOM%$spacing))
				case $rand in
					0)
						printf "${colors[$RANDOM%$colorcount]}${chars[$RANDOM%$count]} "
						;;
					1)
						printf "  "
						;;
					*)
						printf "\033[2C"
						;;
				esac
			done
			printf "\n"

			# sleep .005
		done
		tput cup 0 0
	done