Use em for controls

sass/elements/button.sass

@@ -1,37 +1,22 @@
 =button-small
   border-radius: $radius-small
-  font-size: 11px
-  height: 24px
-  line-height: 16px
-  padding-left: 6px
-  padding-right: 6px
+  font-size: $size-small
 =button-medium
-  font-size: 18px
-  height: 40px
-  padding-left: 14px
-  padding-right: 14px
+  font-size: $size-medium
 =button-large
-  font-size: 22px
-  height: 48px
-  padding-left: 20px
-  padding-right: 20px
+  font-size: $size-large
 
 .button
   +control
   +unselectable
   cursor: pointer
   justify-content: center
-  padding-left: 10px
-  padding-right: 10px
+  padding-left: 1em
+  padding-right: 1em
   text-align: center
   white-space: nowrap
   strong
     color: inherit
-  small
-    display: block
-    font-size: $size-small
-    line-height: 1
-    margin-top: 5px
   .icon,
   .tag
     &:first-child