BASH GAMES: Bash Invaders

Below is the script I have found when trying to manage asynchronous call under bash.
Use J K L keys to navigate and shoot.

#!/bin/bash
if [[ $1 != "" ]]
then
cat << END
BashInvaders!
by Vidar 'koala_man' Holen
www.vidarholen.net

Originally an entry in the #linux.no 1KiB compo (thus the ugly source)
This is a pre-trim version with colors and proper tmp files. All bash. 
Released under the GNU General Public License.

Control your ship with J and L, shoot with K. 
Quit with Q or sigint.

Requires mktemp and sleep with fractions. 

END
exit 0
fi

tput civis

cd /tmp
e=echo
c=clear
r=return
E="$e -ne "
A=$E\\033[
m() { $A$2\;$1\H
}
f() { $A\1\;3$2\m
}

trap z=SigInt SIGINT
 g() {
 $e ${K[$(($2*8+$1))]}
}
 s() {
 K[$(($2*8+$1))]=$3
}
 u() {
 [ $T = 0 ] && $r 0
 m $S $((--T))
 $E `f 3`"."
 x=$((S-Y))
 y=$((T-Z))
 [ $((y%3)) = 0 -a $((x%6)) -lt 4 ] || $r 0
 : $((y/=3)) $((x/=6))
 [ "`g $x $y`" = 1 -a $x -le $o -a $x -ge $n -a $y -le $q -a $y -ge 0 ] || $r 0
 [ $Q = 1 ] && z="You win!"
 s $x $y 0 
 : $((Q--))
 T=0
 $r 1
}
 a() {
 w n +
 w o - 
 h 
}
 w() {
 d=0
 for (( I=0; I<=q; I++ )) {
  [ `g $(($1)) $I` = 1 ] && D=1
 }
 [ $D = 0 ] && : $(($1$2=1)) 
}
 h() {
for (( I=q; I>=0; I--)) {
for (( J=n; J<=o; J++)) {
   [ `g $J $I` = 1 ] && q=$I &&  $r
  }
 }
 }
 
 j() { 
 while read -n 1 S >/dev/null 2>&1
do
$e $S > $M
done
}

G=`mktemp`
L=`mktemp`
M=`mktemp`
N=`mktemp`
X=40
n=0
o=7
q=2
T=0
Y=2
Z=2
U=2
W=0
for (( Q=0; Q<24; Q++)) { 
 K[$Q]=1
}

j 0<&0 &
B=$!

until [ "$z" ]
do
 : $((W++)) 
 if [ -f $M ] 
 then
  i=$(<$M)
  rm $M
  case "$i" in
   q) z="Quit" ;;
   j) X=$(($X-3)) ;;
   l) X=$(($X+3)) ;;
   k) [ $T = 0 ] && S=$((X+1)) && T=22 
   ;;
  esac
 fi
 rm $N  
 exec > $N
for (( J=0; J<=q; J++)) { 
  for (( I=n; I<=o; I++)) { 
   [ `g $I $J` = 1 ] && m $((I*6+Y)) $((J*3+Z)) && $e `f 4`/00\\
  }
 }
 m $X 23
 $e `f 2`"/|\\"
 [ $T != 0 ] && u  
 a
 m 0 0
 exec > `tty`
$c
cat $N
sleep .1
[ $((W%2)) = 0 ] && : $((Y+=U)) && if [ $((Y+n*6)) -lt 2 -o $((Y+o*6)) -gt 75 ] 
then 
: $((U=-U))  $((Z+=2))
[ $((Z+q*3)) -le 20 ] || z="You lose!"
fi
done

$c
$e $z
rm $G $L $M $N $F &> /dev/null
kill $B