Stopwatch { layout: horizontal; background: $boost; height: 5; padding: 1; margin: 1; } Stopwatch.active { background: red; background: $background-lighten-3; } TimeDisplay { content-align: center middle; text-opacity: 60%; height: 3; } Button { width: 16; } #start { dock: left; } #stop { dock: left; display: none; } #reset { dock: right; } .started { text-style: bold; background: $success; color: $text; } .started TimeDisplay { text-opacity: 100%; } .started #start { display: none } .started #stop { display: block } .started #reset { visibility: hidden }