function draws(x,y){
//var my_gradient=ctx.createLinearGradient(0,0,0,100);
//my_gradient.addColorStop(0,"white");
//my_gradient.addColorStop(1,"red");
context.fillStyle = '#1aad19';// 矩形顏色
context.clearRect(0, 0, width, height);
//window.screen.height; //獲取屏幕分辨率的高
//window.screen.width; //獲取屏幕分辨率的寬
//window.screen.availHeight; //獲取屏幕可用工作區的高
//window.screen.availWidth; //獲取屏幕可用工作區的寬
context.fillRect(window.screen.width /2, 0, x, y) ;// 矩形左上角頂點爲(0, 0),右下角頂點爲(100, 100)
}