#!/bin/bash
clear;x=$(($COLUMNS/2)); y=$LINES;unset spacesused[*];declare -a spacesused;xdir=0;ydir=-1;while true ; do read -s -r -t0.02 -n3 direction ; case "${direction:2:1}" in A) ydir=-1;xdir=0 ;; B)ydir=1;xdir=0 ;; C) ydir=0;xdir=1 ;; D) ydir=0;xdir=-1 ;; esac ; space=$(( $COLUMNS * $y + $x )) ; if [[ "${spacesused[$space]}" == "1" || $x -gt $COLUMNS || $x -lt 0 || $y -gt $LINES || $y -lt 0 ]]; then printf '\033[%d;%dHBOOM!\nEND OF LINE.\n' $y $x; break ; else spacesused[$space]=1 ; fi ; ox=$x; oy=$y ; x=$(( $x + $xdir )) ; y=$(( $y + $ydir )) ; printf "\033[%s;%sH\033[46m \033[0m\033[%s;%sH\033[44m \033[0m\033[0;0H" $y $x $oy $ox ; sleep 0.01 ; done