*{margin:0;padding:0;box-sizing:border-box}body{font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:#fafafa}.app-container{min-height:100vh}.app-nav{position:-webkit-sticky;position:sticky;top:60px;display:flex;background:#fff;z-index:999;box-shadow:0 2px 10px rgba(0,0,0,.1)}.nav-btn{flex:1 1;padding:1rem;border:none;background:none;cursor:pointer}.nav-btn.active{background:#0070f3;color:#fff}