snakealgorithm.txt

    <script>
        window.onload=function(){
            canv = document.getElementById("gc");
            ctx = canv.getContext("2d");
            document.addEventListener("keydown",keyPush);
            setInterval(game,1000/15);
        }
        px = py = 10;
        gs = tc = 20;
        ax = ay = 15;
        xv = yv = 0;
        trail=[];
        tail = 5;
        function keyPush(e) {
            switch(e.keyCode){
                case 37:
                    xv=-1;yv=0;
                    break;
                case 38:
                    xv=0;yv=-1;
                    break;
                case 39:
                    xv=1;yv=0;
                    break;
                case 40:
                    xv=0;yv=1;
                    break;
            }
            
        }
        function game() {
            px += xv;
            py += yv;
            if(px<0) {
                px = tc-1;
            }
            if(px>tc-1) {
                px = 0;
            }
            if(py<0) {
                py = tc-1;
            }
            if(py > tc-1) {
                py = 0;
            }
            ctx.fillStyle = "black";
            ctx.fillRect(0,0,canv.width,canv.height);

            ctx.fillStyle = "lime";
            for(var i = 0; i <trail.length; i++) {
                ctx.fillRect(trail[i].x*gs,trail[i].y*gs,gs-2,gs-2);

                if (trail[i].x==px && trail[i].y==py) {
                    tail = 5;
                }
            }
            trail.push ({x:px,y:py});
            while (trail.length>tail) {
                trail.shift();
            }
            if (ax==px && ay==py) {
                tail++;
                ax=Math.floor(Math.random()*tc);
                ay=Math.floor(Math.random()*tc);
            }
            ctx.fillStyle="red";
            ctx.fillRect(ax*gs,ay*gs,gs-2,gs-2);
        }
    </script>