<HTML>
<body>
<h1>CHECKERS</h1>
<h2>Project on AI</h2>
<p>
</p>
<script language="JavaScript1.1">
//Defining variables and object functions.
var red = -1; // player is black
var black = 1; // computer is red
var block_length = 45;
var piece_toggled = false;
var my_turn = true;0
var double_jump = false;
var comp_move = false;
var game_is_over = false;
var safe_from = safe_to = null;
var togglers = 0;
function Coord(x,y) {
this.x = x;
this.y = y;
}
function coord(x,y) {
c = new Coord(x,y);
return c;
}
function integ(num) {
if (num != null)
return Math.round(num);
else
return null;
}
function abs(num) {
return Math.abs(num);
}
function sign(num) {
if (num < 0) return -1;
else return 1;
}
//Load up the Board array.
function Board() {
board = new Array();
for (var i=0;i<8; i++) {
board[i] = new Array();
for (var j=0;j<8;j++)
board[i][j] = Board.arguments[8*j+i];
}
board[-2] = new Array(); // prevents errors
board[-1] = new Array(); // prevents errors
board[8] = new Array(); // prevents errors
board[9] = new Array(); // prevents errors
}
var board;
Board(1,0,1,0,1,0,1,0,
0,1,0,1,0,1,0,1,
1,0,1,0,1,0,1,0,
0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,
0,-1,0,-1,0,-1,0,-1,
-1,0,-1,0,-1,0,-1,0,
0,-1,0,-1,0,-1,0,-1);
function moveable_space(i,j) {
return (((i%2)+j)%2 == 0); //Returns true if space is movable else false, adding array index odd=nonmovable.
}
//Load or Create the main table.
document.write("<table border=1 cellspacing=0 cellpadding=0 width="+(block_length*8+8) +" ");
for(var j=0;j<8;j++) {
document.write("<tr><td><img src='whit.gif' width=4 height="+block_length+">");
for(var i=0;i<8;i++) {
if (moveable_space(i,j))
document.write("<a href='javascript:clicked("+i+","+j+")'>"); //Assign Clicked() fucntion to every white array
document.write("<img src='");
if (board[i][j]==1) document.write("you1.gif");
else if (board[i][j]==-1) document.write("me1.gif");
else if (moveable_space(i,j)) document.write("whit.gif");
else document.write("black.gif");
document.write("' width="+block_length+" height="+block_length
+" name='space"+i+""+j+"' border=0>");
if (moveable_space(i,j)) document.write("</a>");
}
document.write("<img src='black.gif' width=4 height="+block_length+"></td></tr>");
}
document.write("</table><br>"
+"<form name='disp'><input "
+"type=button value=\"Play Again\" onClick=\"location.href+=''\"></form>");
function clicked(i,j) {
if (my_turn) {
if (integ(board[i][j])==1) toggle(i,j);
else if (piece_toggled) move(selected,coord(i,j));
}
}
//Change the colour of a block as selected ,green
function toggle(x,y) {
if (my_turn) {
if (piece_toggled)
draw(selected.x,selected.y,"you1"+((board[selected.x][selected.y]==1.1)?"k":"")+".gif");
if (piece_toggled && (selected.x == x) && (selected.y == y)) {
piece_toggled = false;
if (double_jump) { my_turn = double_jump = false; computer(); }
} else {
piece_toggled = true;
draw(x,y,"you2"+((board[x][y]==1.1)?"k":"")+".gif");
}
selected = coord(x,y);
}
else {
if ((piece_toggled) && (integ(board[selected_c.x][selected_c.y])==-1))
draw(selected_c.x,selected_c.y,"me1"+((board[selected_c.x][selected_c.y]==-1.1)?"k":"")+".gif");
if (piece_toggled && (selected_c.x == x) && (selected_c.y == y)) {
piece_toggled = false;
} else {
piece_toggled = true;
draw(x,y,"me2"+((board[x][y]==-1.1)?"k":"")+".gif");
}
selected_c = coord(x,y);
}
}
function draw(x,y,name) {
document.images["space"+x+""+y].src = name;
}
function legal_move(from,to) {
if ((to.x < 0) || (to.y < 0) || (to.x > 7) || (to.y > 7)) return false;
piece = board[from.x][from.y];
distance = coord(to.x-from.x,to.y-from.y);
if ((distance.x == 0) || (distance.y == 0)) {
alert("You may only move diagonally.");
return false;
}
if (abs(distance.x) != abs(distance.y)) {
alert("Invalid move.");
return false;
}
if (abs(distance.x) > 2) {
alert("Invalid move.");
return false;
}
if ((abs(distance.x) == 1) && double_jump) {
return false;
}
if ((board[to.x][to.y] != 0) || (piece == 0)) {
return false;
}
if ((abs(distance.x) == 2)
&& (integ(piece) != -integ(board[from.x+sign(distance.x)][from.y+sign(distance.y)]))) {
return false;
}
if ((integ(piece) == piece) && (sign(piece) != sign(distance.y))) {
return false;
}
return true;
}
function move(from,to) {
my_turn = true;
if (legal_move(from,to)) {
piece = board[from.x][from.y];
distance = coord(to.x-from.x,to.y-from.y);
if ((abs(distance.x) == 1) && (board[to.x][to.y] == 0)) {
swap(from,to);
} else if ((abs(distance.x) == 2)
&& (integ(piece) != integ(board[from.x+sign(distance.x)][from.y+sign(distance.y)]))) {
double_jump = false;
swap(from,to);
remove(from.x+sign(distance.x),from.y+sign(distance.y));
if ((legal_move(to,coord(to.x+2,to.y+2)))
|| (legal_move(to,coord(to.x+2,to.y-2)))
|| (legal_move(to,coord(to.x-2,to.y-2)))
|| (legal_move(to,coord(to.x-2,to.y+2)))) {
double_jump = true;
alert("You may complete the double jump or click on your piece to stay still.");
}
}
if ((board[to.x][to.y] == 1) && (to.y == 7)) king_me(to.x,to.y);
selected = to;
if (game_over() && !double_jump) {
setTimeout("toggle("+to.x+","+to.y+");my_turn = double_jump = false;computer(); ",1000);
}
}
return true;
}
function king_me(x,y) {
if (board[x][y] == 1) {
board[x][y] = 1.1; // king you
draw(x,y,"you2k.gif");
} else if (board[x][y] == -1) {
board[x][y] = -1.1; // king me
draw(x,y,"me2k.gif");
}
}
function swap(from,to) {
if (my_turn || comp_move) {
dummy_src = document.images["space"+to.x+""+to.y].src;
document.images["space"+to.x+""+to.y].src = document.images["space"+from.x+""+from.y].src;
document.images["space"+from.x+""+from.y].src = dummy_src;
}
dummy_num = board[from.x][from.y];
board[from.x][from.y] = board[to.x][to.y];
board[to.x][to.y] = dummy_num;
}
function remove(x,y) {
if (my_turn || comp_move)
draw(x,y,"whit.gif");
board[x][y] = 0;
}
function move_comp(from,to) {
toggle(from.x,from.y);
comp_move = true;
swap(from,to);
if (abs(from.x-to.x) == 2) {
remove(from.x+sign(to.x-from.x),from.y+sign(to.y-from.y));
}
if ((board[to.x][to.y] == -1) && (to.y == 0)) king_me(to.x,to.y);
setTimeout("selected_c = coord("+to.x+","+to.y+");piece_toggled = true;",900);
setTimeout("bak=my_turn;my_turn=false;toggle("+to.x+","+to.y+");my_turn=bak;",1000);
if (game_over()) {
setTimeout("comp_move = false;my_turn = true;togglers=0;",600);
}
return true;
}
function game_over() { // make sure game is not over (return false if game is over)
comp = you = false;
for(var i=0;i<8;i++) {
for(var j=0;j<8;j++) {
if(integ(board[i][j]) == -1) comp = true;
if(integ(board[i][j]) == 1) you = true;
}
}
if (!comp) alert("You Win!!");
if (!you) alert("You Lose!!");
game_is_over = (!comp || !you)
return (!game_is_over);
}
function computer() {
// step one - prevent any jumps
for(var j=0;j<8;j++) {
for(var i=0;i<8;i++) {
if (integ(board[i][j]) == 1) {
if ((legal_move(coord(i,j),coord(i+2,j+2))) && (prevent(coord(i+2,j+2),coord(i+1,j+1)))) {
return true;
} if ((legal_move(coord(i,j),coord(i-2,j+2))) && (prevent(coord(i-2,j+2),coord(i-1,j+1)))) {
return true;
}
} if (board[i][j] == 1.1) {
if ((legal_move(coord(i,j),coord(i-2,j-2))) && (prevent(coord(i-2,j-2),coord(i-1,j-1)))) {
return true;
} if ((legal_move(coord(i,j),coord(i+2,j-2))) && (prevent(coord(i+2,j-2),coord(i+1,j-1)))) {
return true;
}
}
}
}
// step two - if step one not taken, look for jumps
for(var j=7;j>=0;j--) {
for(var i=0;i<8;i++) {
if (jump(i,j))
return true;
}
}
safe_from = null;
// step three - if step two not taken, look for safe single space moves
for(var j=0;j<8;j++) {
for(var i=0;i<8;i++) {
if (single(i,j))
return true;
}
}
// if no safe moves, just take whatever you can get
if (safe_from != null) {
move_comp(safe_from,safe_to);
} else {
alert("You win!!");
game_is_over = true;
}
safe_from = safe_to = null;
return false;
}
function jump(i,j) {
if (board[i][j] == -1.1) {
if (legal_move(coord(i,j),coord(i+2,j+2))) {
move_comp(coord(i,j),coord(i+2,j+2));
setTimeout("jump("+(i+2)+","+(j+2)+");",500);
return true;
} if (legal_move(coord(i,j),coord(i-2,j+2))) {
move_comp(coord(i,j),coord(i-2,j+2));
setTimeout("jump("+(i-2)+","+(j+2)+");",500);
return true;
}
} if (integ(board[i][j]) == -1) {
if (legal_move(coord(i,j),coord(i-2,j-2))) {
move_comp(coord(i,j),coord(i-2,j-2));
setTimeout("jump("+(i-2)+","+(j-2)+");",500);
return true;
} if (legal_move(coord(i,j),coord(i+2,j-2))) {
move_comp(coord(i,j),coord(i+2,j-2));
setTimeout("jump("+(i+2)+","+(j-2)+");",500);
return true;
}
}
return false;
}
function single(i,j) {
if (board[i][j] == -1.1) {
if (legal_move(coord(i,j),coord(i+1,j+1))) {
safe_from = coord(i,j);
safe_to = coord(i+1,j+1);
if (wise(coord(i,j),coord(i+1,j+1))) {
move_comp(coord(i,j),coord(i+1,j+1));
return true;
}
} if (legal_move(coord(i,j),coord(i-1,j+1))) {
safe_from = coord(i,j);
safe_to = coord(i-1,j+1);
if (wise(coord(i,j),coord(i-1,j+1))) {
move_comp(coord(i,j),coord(i-1,j+1));
return true;
}
}
} if (integ(board[i][j]) == -1) {
if (legal_move(coord(i,j),coord(i+1,j-1))) {
safe_from = coord(i,j);
safe_to = coord(i+1,j-1);
if (wise(coord(i,j),coord(i+1,j-1))) {
move_comp(coord(i,j),coord(i+1,j-1));
return true;
}
} if (legal_move(coord(i,j),coord(i-1,j-1))) {
safe_from = coord(i,j);
safe_to = coord(i-1,j-1);
if (wise(coord(i,j),coord(i-1,j-1))) {
move_comp(coord(i,j),coord(i-1,j-1));
return true;
}
}
}
return false;
}
function possibilities(x,y) {
if (!jump(x,y))
if (!single(x,y))
return true;
else
return false;
else
return false;
}
function prevent(end,s) {
i = end.x;
j = end.y;
if (!possibilities(s.x,s.y))
return true;
else if ((integ(board[i-1][j+1])==-1) && (legal_move(coord(i-1,j+1),coord(i,j)))) {
return move_comp(coord(i-1,j+1),coord(i,j));
} else if ((integ(board[i+1][j+1])==-1) && (legal_move(coord(i+1,j+1),coord(i,j)))) {
return move_comp(coord(i+1,j+1),coord(i,j));
} else if ((board[i-1][j-1]==-1.1) && (legal_move(coord(i-1,j-1),coord(i,j)))) {
return move_comp(coord(i-1,j-1),coord(i,j));
} else if ((board[i+1][j-1]==-1.1) && (legal_move(coord(i+1,j-1),coord(i,j)))) {
return move_comp(coord(i+1,j-1),coord(i,j));
} else {
return false;
}
}
function wise(from,to) {
i = to.x;
j = to.y;
n = (j>0);
s = (j<7);
e = (i<7);
w = (i>0);
if (n&&e) ne = board[i+1][j-1]; else ne = null;
if (n&&w) nw = board[i-1][j-1]; else nw = null;
if (s&&e) se = board[i+1][j+1]; else se = null;
if (s&&w) sw = board[i-1][j+1]; else sw = null;
eval(((j-from.y != 1)?"s":"n")+((i-from.x != 1)?"e":"w")+"=0;");
if ((sw==0) && (integ(ne)==1)) return false;
if ((se==0) && (integ(nw)==1)) return false;
if ((nw==0) && (se==1.1)) return false;
if ((ne==0) && (sw==1.1)) return false;
return true;
}
alert("Start the Game, select your piece to move.");
my_turn = true;
// -->
</script>
</body>
</html>
