<!-- //
step = 0;
diff=3;
function clear_all(form) {
step = 0;
for (i=0;i<9; ++i) {
position="a"+i;
form[position].value="";
   }
}
function clickit(field) {
if (step == -1) {alert("Reset to play again"); return;}
position=field.name.substring(1,2,1);
position = 'a'+position;
if (field.form[position].value !="") {alert("Can't go there"); return;}
field.form[position].value="X";
if (eval_pos(field.form)) {
field.form.output.value="You Win!";
step = -1;
return;
}
position=get_move(field.form);
field.form.output.value='I moved to ' + position.substring(1,2,1);
if (position=="") {
field.form.output.value="No Winner.";
step = -1;
return;
}
field.form[position].value="O";
if (eval_pos(field.form)) {
field.form.output.value="You Lose!";
step = -1;
   }
}
function eval_pos(form) {
if ((form.a0.value!="" && form.a0.value==form.a3.value && form.a0.value==form.a6.value)||
(form.a0.value!="" && form.a0.value==form.a1.value && form.a0.value==form.a2.value) ||
(form.a0.value!="" && form.a0.value==form.a4.value && form.a0.value==form.a8.value) ||
(form.a1.value!="" && form.a1.value==form.a4.value && form.a1.value==form.a7.value) ||
(form.a2.value!="" && form.a2.value==form.a5.value && form.a2.value==form.a8.value) ||
(form.a2.value!="" && form.a2.value==form.a4.value && form.a2.value==form.a6.value) ||
(form.a3.value!="" && form.a3.value==form.a4.value && form.a3.value==form.a5.value) ||
(form.a6.value!="" && form.a6.value==form.a7.value && form.a6.value==form.a8.value))
return true;
else
return false;
}
function f(a) {
if (a =="") return "."; else return a;
}
function comp_move(form,player,weight,depth) {
var cost;
var bestcost=-2;
var position;
var newplayer;
if (player=="X") newplayer="O"; else newplayer="X";
if (depth==diff) return 0;
if (eval_pos(form)) return 1;
for (var i=0; i<9; ++i) {
position='a'+i;
if (form[position].value !="")
continue;
form[position].value=player;
cost = comp_move(form,newplayer, -weight, depth+1);
if (cost > bestcost) {
bestcost=cost;
if (cost==1) i=9;
}
form[position].value="";
}
if (bestcost==-2) bestcost=0;
return(-bestcost);
}
function get_move(form) {
var cost;
var bestcost=-2;
bestmove="";
if (step++ == 0)
if (form.a4.value=="")
return "a4";
else
if (form.a0.value=="")
return "a0";
for (var i=0; i<9; ++i) {
localposition='a'+i;
if (form[localposition].value !="")
continue;
form[localposition].value="O";
cost=comp_move(form,"X", -1, 0);
if (cost > bestcost) {
if (cost==1) i=9;
bestmove=localposition;
bestcost=cost;
}
form[localposition].value="";
}
return bestmove;
}
function complain(field) {
field.form.output.focus();
alert("Don't change the game fields directly!");
}
// -->