body,html{background:#f5f5f5;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,sans-serif;margin:0;padding:0}.app-container{display:flex;flex-direction:column;min-height:100vh}.app-header{background:#2c3e50;color:#fff;padding:1rem;text-align:center}.app-header h1{font-size:2rem;margin:0}.app-main{flex:1;padding:2rem}