Programmer Assistant: Snake Game

Source:
<div id="sceneContainer" align="center"></div>
<script type="text/javascript">
var tbl;
var lblScore;
var lblExtraFood;
var severitySelect;
var maxX = 20;
var maxY = 20;
var endGame = false;
var score = 0;
var exteraFood = null;
var canExtraFood = true;
var currentPosX = parseInt(maxX / 2);
var currentPosY = parseInt(maxY / 2);
var colors = ["red", "green", "blue", "cyan", "brown", "yellow" , "cyan", "blue", "red", "green", "cyan", "brown", "yellow" , "cyan", "purple"];
var currentDirection = 6; // 6 -> right | 8 -> up | 4 -> left | 2 -> down
function appendToScene(el) {
    document.getElementById("sceneContainer").appendChild(el);
}
function createScene() {
    severitySelect = document.createElement("select");
    appendToScene(severitySelect);
    var easy = document.createElement("option");
    easy.innerHTML = "easy";
    easy.value = 250;

    var medium = document.createElement("option");
    medium.innerHTML = "medium";
    medium.value = 150;

    var hard = document.createElement("option");
    hard.innerHTML = "hard";
    hard.value = 50;

    severitySelect.appendChild(easy);
    severitySelect.appendChild(medium);
    severitySelect.appendChild(hard);

    tbl = document.createElement("table");
    tbl.style.borderColor = "black";
    tbl.style.borderWidth = "1px";
    tbl.style.borderStyle = "solid";
    tbl.style.width = "200px";
    tbl.style.height = "200px";
    var tbody = document.createElement("tbody");
    tbl.appendChild(tbody);
    for (var i = 0; i <= maxX; i ++) {
        var tr = document.createElement("tr");
        tbody.appendChild(tr);
        for (var j = 0; j <= maxY; j ++) {
            var td = document.createElement("td");
            tr.appendChild(td);
            td.style.fontSize = "4px";
            td.innerHTML = " ";
            td.player = false;
            td.food = false;
            td.score = 0;
            td.currentX = i;
            td.currentY = j;
            td.nextCell = null;
        }
    }
    appendToScene(tbl);

    lblScore = document.createElement("span");
    lblScore.innerHTML = score;
    var div = document.createElement("div");
    var scoreLabel = document.createElement("span");
    scoreLabel.innerHTML = "score : ";
    div.appendChild(scoreLabel);
    div.appendChild(lblScore);
    lblExtraFood = document.createElement("span");
    div.appendChild(lblExtraFood);
    appendToScene(div);

    var copyRightDiv = document.createElement("div");
    appendToScene(copyRightDiv);
    copyRightDiv.style.textAlign = "center";
    copyRightDiv.innerHTML = "Powered by <a href='mailto:mostafarastgar@gmail.com'>Mostafa Rastegar</a>";
}

function addSubtractX(x, count, as) {
    if (as == "a") {
        if (x + count > maxX) {
            return (x + count) - maxX - 1;
        }
        else {
            return x + count
        }
    }
    else {
        if (x - count < 0) {
            return maxX - (count - x) + 1;
        }
        else {
            return x - count;
        }
    }
}
function addSubtractY(y, count, as) {
    if (as == "a") {
        if (y + count > maxY) {
            return (y + count) - maxY - 1;
        }
        else {
            return y + count
        }
    }
    else {
        if (y - count < 0) {
            return maxY - (count - y) + 1;
        }
        else {
            return y - count;
        }
    }
}
function canChangeDirection(newDirection) {
    if ((currentDirection == 6 && newDirection == 4) || (currentDirection == 8 && newDirection == 2) || (currentDirection == 4 && newDirection == 6) || (currentDirection == 2 && newDirection == 8))
        return false;
    else
        return true;
}
function colorPlayer() {
    var cell0 = tbl.rows[currentPosX].cells[currentPosY];
    cell0.style.backgroundColor = "brown";
    cell0.player = true;

    var cell1 = tbl.rows[currentPosX].cells[addSubtractY(currentPosY, 1, "s")];
    cell1.style.backgroundColor = "black";
    cell1.player = true;
    cell0.nextCell = cell1;

    var cell2 = tbl.rows[currentPosX].cells[addSubtractY(currentPosY, 2, "s")];
    cell2.style.backgroundColor = "black";
    cell2.player = true;
    cell1.nextCell = cell2;

    var cell3 = tbl.rows[currentPosX].cells[addSubtractY(currentPosY, 3, "s")];
    cell3.style.backgroundColor = "black";
    cell3.player = true;
    cell2.nextCell = cell3;

    cell3.nextCell = null;
}

function gameOver() {
    endGame = true;
    var div = document.createElement("div");
    div.style.opacity = "0.4";
    div.style.filter = "alpha(opacity:40)";
    colorDiv(div);
    div.style.width = "100%";
    div.style.height = "100%";
    div.style.textAlign = "center";
    div.innerHTML = " ";
    appendToScene(div);
    div.style.position = "absolute";
    div.style.top = "0px";
    div.style.left = "0px";

    var goDiv = document.createElement("div");
    goDiv.innerHTML = "GAME OVER";
    goDiv.style.position = "absolute";
    goDiv.style.top = "50%";
    goDiv.style.left = "50%";
    appendToScene(goDiv);

}
function colorDiv(div) {
    if (div.style.backgroundColor == "red")
        div.style.backgroundColor = "green";
    else if (div.style.backgroundColor == "green")
        div.style.backgroundColor = "blue";
    else
        div.style.backgroundColor = "red";
    setTimeout(function() {
        colorDiv(div);
    }, 1000);
}
function carryPlayer() {
    if (!endGame) {
        moveCell(tbl.rows[currentPosX].cells[currentPosY], null, null);
        setTimeout(function() {
            carryPlayer();
        }, severitySelect.value);
    }
}
function makeFood() {
    var y = 0;
    var x = 0;
    do{
        var d = new Date();
        x = d.getMilliseconds() % (maxX + 1)
        y = d.getMilliseconds() % (maxY + 1)
    } while (tbl.rows[x].cells[y].player == true)
    tbl.rows[x].cells[y].food = true;
    if (score == 0 || score % 10 != 0 || !canExtraFood) {
        tbl.rows[x].cells[y].style.backgroundColor = "green";
        tbl.rows[x].cells[y].score = 1;
        canExtraFood = true;
    } else {
        tbl.rows[x].cells[y].score = 10;
        exteraFood = tbl.rows[x].cells[y];
        setTimer(15);
    }
}
function setTimer(leftTime) {
    if (!endGame) {
        lblExtraFood.innerHTML = "";
        if (exteraFood != null) {
            if (leftTime == 0) {
                exteraFood.food = false;
                exteraFood.style.backgroundColor = "";
                exteraFood.score = 0;
                exteraFood = null;
                canExtraFood = false;
                makeFood();
            } else {
                lblExtraFood.innerHTML = "    " + leftTime;
                exteraFood.style.backgroundColor = colors[leftTime - 1];
                setTimeout(function() {
                    setTimer(leftTime - 1)
                }, severitySelect.value);
            }
        }
    }
}
function init() {
    createScene();
    colorPlayer();
    carryPlayer();
    makeFood();
    document.onkeydown = function movePlayer(event) {
        var event = document.all ? window.event : event;
        if (!endGame) {
            if (event.keyCode == 37) {
                if (canChangeDirection(4)) {
                    currentDirection = 4;
                    moveCell(tbl.rows[currentPosX].cells[currentPosY], null, null);
                }
            }
            if (event.keyCode == 38) {
                if (canChangeDirection(8)) {
                    currentDirection = 8;
                    moveCell(tbl.rows[currentPosX].cells[currentPosY], null, null);
                }
            }
            if (event.keyCode == 39) {
                if (canChangeDirection(6)) {
                    currentDirection = 6;
                    moveCell(tbl.rows[currentPosX].cells[currentPosY], null, null);
                }
            }
            if (event.keyCode == 40) {
                if (canChangeDirection(2)) {
                    currentDirection = 2;
                    moveCell(tbl.rows[currentPosX].cells[currentPosY], null, null);
                }
            }
        }
        if (event.keyCode == 27) {
            alert("waiting ...");
        }
	return false;
    }
}

function addScore(scoreAmount) {
    score = score + scoreAmount;
    lblScore.innerHTML = score;
}

function cutCell(newCell, oldCell) {
    newCell.player = oldCell.player;
    newCell.style.backgroundColor = oldCell.style.backgroundColor;

    return newCell;
}
function getDirection(cell, preCellOld) {
    if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")] == preCellOld)
        return 6;
    else if (tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY] == preCellOld)
        return 8;
    else if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")] == preCellOld)
            return 4;
        else
            return 2;
}
function moveCell(cell, preCell, preCellOld) {
    var newCell;
    var food = false;
    if (preCell == null) {
        if (currentDirection == 6) {
            if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")].player == true) {
                gameOver();
                return;
            }
            if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")].food == true) {
                tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")].food = false;
                food = true;
            }
            newCell = cutCell(tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")], cell);
            currentPosY = addSubtractY(currentPosY, 1, "a");
        } else if (currentDirection == 8) {
            if (tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY].player == true) {
                gameOver();
                return;
            }
            if (tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY].food == true) {
                tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY].food = false;
                food = true;
            }
            newCell = cutCell(tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY], cell);
            currentPosX = addSubtractX(currentPosX, 1, "s");
        } else if (currentDirection == 4) {
            if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")].player == true) {
                gameOver();
                return;
            }
            if (tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")].food == true) {
                tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")].food = false;
                food = true;
            }
            newCell = cutCell(tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")], cell);
            currentPosY = addSubtractY(currentPosY, 1, "s");
        } else {
            if (tbl.rows[addSubtractX(cell.currentX, 1, "a")].cells[cell.currentY].player == true) {
                gameOver();
                return;
            }
            if (tbl.rows[addSubtractX(cell.currentX, 1, "a")].cells[cell.currentY].food == true) {
                tbl.rows[addSubtractX(cell.currentX, 1, "a")].cells[cell.currentY].food = false;
                food = true;
            }
            newCell = cutCell(tbl.rows[addSubtractX(cell.currentX, 1, "a")].cells[cell.currentY], cell);
            currentPosX = addSubtractX(currentPosX, 1, "a");
        }
    } else {
        switch (getDirection(cell, preCellOld)) {
            case 6:
                newCell = cutCell(tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "a")], cell);
                break;
            case 8:
                newCell = cutCell(tbl.rows[addSubtractX(cell.currentX, 1, "s")].cells[cell.currentY], cell);
                break;
            case 4:
                newCell = cutCell(tbl.rows[cell.currentX].cells[addSubtractY(cell.currentY, 1, "s")], cell);
                break;
            default:
                newCell = cutCell(tbl.rows[addSubtractX(cell.currentX, 1, "a")].cells[cell.currentY], cell);
        }
        preCell.nextCell = newCell;
    }
    if (food == true) {
        newCell.nextCell = cell;
        cell.player = true;
        cell.style.backgroundColor = "black";
        addScore(newCell.score);
        if (newCell.score > 1)
            canExtraFood = false;
        newCell.food = false;
        newCell.score = 0;
        exteraFood = null;
        makeFood();
    } else {
        if (cell.nextCell != null)
            moveCell(cell.nextCell, newCell, cell);
        else {
            cell.player = false;
            newCell.nextCell = null;
            cell.style.backgroundColor = "";
        }
    }
}
init();
</script>
Pages

Snake Game
