這是CSS代碼：

body{????padding:?20px;}
.all_bg?{????
display:?inline-block;????
width:?800px;????
height:?600px;????
position:?relative;
}
.all_bg?.allCanvas?{????
position:?relative;????
width:?800px;????
height:?600px;????
margin:?0;
}
#canvas1?{????
position:?absolute;????
top:?0;????
left:?0;????
z-index:?1;
}
#canvas2?{????
position:?absolute;????
top:?0;????
left:?0;????
z-index:?0;
}

大魚的JS代碼：

var?bigFishObj?=?function(){????
this.x;????
this.y;????
this.bigEye?=?new?Image();????
this.bigBody?=?new?Image();????
this.bigTail?=?new?Image();
}
bigFishObj.prototype.init?=?function(){????
this.x?=?canWidth?*?0.5;????
this.y?=?canHeight?*?0.5;????
this.bigEye.src?=?"./src/bigEye0.png";????
this.bigBody.src?=?"./src/bigSwim0.png";????
this.bigTail.src?=?"./src/bigTail0.png";
}
bigFishObj.prototype.drawImage?=?function(){????
ctx1.save();????
ctx1.drawImage(this.bigEye,?this.x,?this.y);????
ctx1.drawImage(this.bigBody,?this.x,?this.y);????
ctx1.drawImage(this.bigTail,?this.x,?this.y);????
ctx1.restore();
}

而且我的canvas1和canvas2不是重疊的，但是看老師演示兩個canvas是重疊在一起的