<script>window.onload = function(){//定义一些公共变量var gj = document.getElementById("gj");var p2 = gj.getContext("2d");//定义蛇的变量var snake = 3;//定义存储蛇身体的数组var sBody = [];//定义蛇的初始化位置(坐标)var x = y = 0;//定义蛇的初始化运动方向var direction = 39;//定义食物的位置var fx = fy =0;//绘制场景(运动场所)var bg = document.getElementById("bg");var p1 = bg.getContext("2d");p1.strokeStyle="#efefef"var bx = 0;var by = 0;for(var i = 0;i<=40;i++){//1.画横线
              by+=10;p1.moveTo(0,by)p1.lineTo(400,by)p1.stroke();//2.画竖线
              bx+=10;p1.moveTo(bx,0)p1.lineTo(bx,400)p1.stroke();}//调用函数
          putFood();var Run = setInterval(sankeRun,160);//随机放食物function putFood(){fx = Math.ceil(Math.random()*40-1)*10;fy = Math.ceil(Math.random()*40-1)*10;p2.fillStyle="#009900";p2.fillRect(fx,fy,10,10);}document.onkeydown = function(){switch(event.keyCode){case 37: direction = 37;break;//左case 38: direction = 38;break;//上case 39: direction = 39;break;//右case 40: direction = 40;break;//下
            }}//蛇运动function sankeRun(){switch(direction){case 37: x -= 10;break;case 38: y -= 10;break;case 39: x += 10;break;case 40: y += 10;break;}//调整蛇的x方向路径
            p2.fillStyle="#ffff66";p2.fillRect(x,y,10,10);    clear();sBody.push({'x':x , 'y':y});bump();}//擦除尾部function clear(){if(sBody.length>snake){var wb = sBody.shift();p2.clearRect(wb.x,wb.y,10,10);}}//碰撞检测function bump(){//撞墙if(x>=400 || y>=400 || x<=-1 || y<=-1){alert("碰壁而死");clearInterval(Run);x = 0;y = 0;    }//撞自己//for(var i=0;i<=sBody.length;i++){//alert(sBody[i].x+"---"+sBody[i].y);//if(sBody[i].x == x && sBody[i].y == y){//alert("自爆而亡");//clearInterval(Run);//x = 0;//y = 0;    //window.location.reload();//刷新页面//}//}//蛇吃食物if(x == fx && y == fy){snake += 1;putFood();}}}    </script>