| // nvue下hover-class无效  | 
| $u-button-before-top:50% !default;  | 
| $u-button-before-left:50% !default;  | 
| $u-button-before-width:100% !default;  | 
| $u-button-before-height:100% !default;  | 
| $u-button-before-transform:translate(-50%, -50%) !default;  | 
| $u-button-before-opacity:0 !default;  | 
| $u-button-before-background-color:#000 !default;  | 
| $u-button-before-border-color:#000 !default;  | 
| $u-button-active-before-opacity:.15 !default;  | 
| $u-button-icon-margin-left:4px !default;  | 
| $u-button-plain-u-button-info-color:$u-info;  | 
| $u-button-plain-u-button-success-color:$u-success;  | 
| $u-button-plain-u-button-error-color:$u-error;  | 
| $u-button-plain-u-button-warning-color:$u-error;  | 
|   | 
| .u-button { | 
|     width: 100%; | 
|      | 
|     &__text { | 
|         white-space: nowrap; | 
|         line-height: 1; | 
|     } | 
|       | 
|     &:before {  | 
|         position: absolute;  | 
|         top:$u-button-before-top;  | 
|         left:$u-button-before-left;  | 
|         width:$u-button-before-width;  | 
|         height:$u-button-before-height;  | 
|         border: inherit;  | 
|         border-radius: inherit;  | 
|         transform:$u-button-before-transform;  | 
|         opacity:$u-button-before-opacity;  | 
|         content: " ";  | 
|         background-color:$u-button-before-background-color;  | 
|         border-color:$u-button-before-border-color;  | 
|     }  | 
|       | 
|     &--active {  | 
|         &:before {  | 
|             opacity: .15  | 
|         }  | 
|     }  | 
|       | 
|     &__icon+&__text:not(:empty),  | 
|     &__loading-text {  | 
|         margin-left:$u-button-icon-margin-left;  | 
|     }  | 
|       | 
|     &--plain {  | 
|         &.u-button--primary {  | 
|             color: $u-primary;  | 
|         }  | 
|     }  | 
|       | 
|     &--plain {  | 
|         &.u-button--info {  | 
|             color:$u-button-plain-u-button-info-color;  | 
|         }  | 
|     }  | 
|       | 
|     &--plain {  | 
|         &.u-button--success {  | 
|             color:$u-button-plain-u-button-success-color;  | 
|         }  | 
|     }  | 
|       | 
|     &--plain {  | 
|         &.u-button--error {  | 
|             color:$u-button-plain-u-button-error-color;  | 
|         }  | 
|     }  | 
|       | 
|     &--plain {  | 
|         &.u-button--warning {  | 
|             color:$u-button-plain-u-button-warning-color;  | 
|         }  | 
|     }  | 
| }  |