*{margin:0;padding:0;box-sizing:border-box}body{background:#111;color:#fff;font-family:Arial;height:100vh;display:flex;flex-direction:column}
.app-header{height:60px;background:#222;display:flex;align-items:center;justify-content:center}#content{flex:1;overflow:auto}
.bottom-nav{display:flex;height:65px;background:#222}.bottom-nav button{flex:1;background:none;border:none;color:#fff}
.bottom-nav .active{color:gold}