var p1x,p1y,p2x,p2y,p3x,p3y;
    var sourX=0,sourY=-1;
    window.onload=function() {
        var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");
        canvas.width = 800;
        canvas.height = 600;
        g=300/30;

        //var R=g*3; //大圆半径300
        //var r=R*(Math.PI*0.135); //小圆半径150
        
        
       drawBackground(context,200,100);

        //context.globalCompositeOperation="destination-over";

       //setInterval(function(){
       //    drawBg(context,200,100);
       //},40);

        drawStar(context,g*3*(Math.PI*0.135),g*3,g*5,g*6,0);

        drawStar(context,g*(Math.PI*0.135),g,g*10,g*3,18);

        drawStar(context,g*(Math.PI*0.135),g,g*12,g*5,36);

        drawStar(context,g*(Math.PI*0.135),g,g*12,g*8,0);

        drawStar(context,g*(Math.PI*0.135),g,g*10,g*10,18);

    }

    function drawBg(cxt,x,y){

        console.log(sum());
        cxt.save();
        cxt.beginPath();
        cxt.moveTo(x,y);
        cxt.fillStyle="red";
        //cxt.bezierCurveTo(x+32, y-26, x+242, y+68, x+300, y+37);
        cxt.bezierCurveTo(x+32, y-26, x+242, y+68, x+300, y+37);
        cxt.lineTo(x+300,y+237);
        cxt.bezierCurveTo(x+162, y+254, x+84, y+138, x, y+174);
        cxt.lineTo(x,y);
        cxt.fill();
        cxt.closePath();
        cxt.restore();

        cxt.beginPath();
        cxt.moveTo(x,y);
        cxt.lineTo(x,y+300);
        cxt.lineWidth=6;
        cxt.lineCap="round";
        cxt.stroke();
        cxt.closePath();
    }

    function drawBackground(cxt,x,y){
        cxt.save();
        cxt.beginPath();
        //cxt.translate(200,100);
        //cxt.bezierCurveTo(x+32, y-26, x+242, y+68, x+300, y+37);
        //cxt.fillStyle="red";
        //cxt.fillRect(200,200,300,200);
        //cxt.fill();
        cxt.moveTo(x,y);
        cxt.fillStyle="red";
        //cxt.bezierCurveTo(x+32, y-26, x+242, y+68, x+300, y+37);
        cxt.bezierCurveTo(x+112, y-26, x+242, y+68, x+300, y+37);
        cxt.lineTo(x+300,y+237);
        cxt.bezierCurveTo(x+162, y+254, x+84, y+138, x, y+174);
        cxt.lineTo(x,y);
        cxt.fill();
        cxt.closePath();
        cxt.restore();

        cxt.beginPath();
        cxt.moveTo(x,y);
        cxt.lineTo(x,y+300);
        cxt.lineWidth=6;
        cxt.lineCap="round";
        cxt.stroke();
        cxt.closePath();
    }

    function drawStar(cxt,r,R,x,y,rot){//x,y偏移量，rot旋转角度（顺时针）
        cxt.save();
        cxt.beginPath();
        cxt.translate(200,100);
        for(var i=0;i<5;i++){
            cxt.lineTo(Math.cos((18+i*72-rot)/180*Math.PI)*R+x,
                            -Math.sin((18+i*72-rot)/180*Math.PI)*R+y);//大圆半径300

            cxt.lineTo(Math.cos((54+i*72-rot)/180*Math.PI)*r+x,
                            -Math.sin((54+i*72-rot)/180*Math.PI)*r+y);//小圆半径150

        }
        cxt.fillStyle="yellow";
        cxt.strokeStyle="#aaa";
        cxt.lineWidth=0.5;
        cxt.fill();
        cxt.stroke();
        cxt.closePath();
        cxt.restore();
    }
	

    function sum(){
        sourX++;
        if(sourX>100){
            sourX=-sourX;
        }
        return sourX;
    }