#canvas{ display: block; margin: 0 auto; }
#controller{ margin: 0 auto; }
.op_btn{ margin: 10px 0 0 10px; border:2px solid #aaa; width:80px; height: 40px; line-height: 40px; font-size: 20px; text-align: center; border-radius:5px 5px; cursor:pointer; background-color: white; font-weight: bold; font-family: Microsoft Yahei,Arial; margin-left: auto;margin-right: auto;margin-top:20px;}
.op_btn:hover{ background-color: #def; }
.clearfix{ clear:both; }

.color_btn{ margin: 10px 10px 0 0; border: 5px solid white; width:40px; height: 40px; border-radius:5px 5px; cursor:pointer; margin-left: auto;margin-right: auto;width:50%;float: left;}
.color_btn:hover{ border: 5px solid violet; }
.color_btn_selected{ border: 5px solid blueviolet; }

#black_btn{ background-color: black; }
#blue_btn{ background-color: blue; }
#green_btn{ background-color: green; }
#red_btn{ background-color: red; }
#orange_btn{ background-color: orange; }
#yellow_btn{ background-color: yellow; }