Button 按钮

<button class="cu-btn">默认</button>
<button class="cu-btn round">圆角</button>
<button class="cu-btn icon">
	<text class="cuIcon-emojifill"></text>
</button>

.cu-btn 
.cu-btn::after
.cu-btn:not([class*="bg-"]) 
.cu-btn[class*="line"] 
.cu-btn[class*="line"]::after
.cu-btn.round[class*="line"]::after 
.cu-btn[class*="lines"]::after 
.cu-btn[class*="bg-"]::after 
.cu-btn.sm 
.cu-btn.lg 
.cu-btn.cuIcon.sm 
.cu-btn.cuIcon 
button.cuIcon.lg 
.cu-btn.shadow-blur::before 
.cu-btn.button-hover 
.block 
.cu-btn.block 
.cu-btn[disabled]

.cu-bar.btn-group
.cu-bar.btn-group button
.cu-bar.btn-group button