*{margin:0;padding:0;box-sizing:border-box}#app{font-family:Arial,sans-serif;min-height:100vh;display:flex;flex-direction:column}header{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff;padding:1rem 2rem;box-shadow:0 2px 4px #0000001a}header h1{margin-bottom:.5rem}nav a{color:#fff;text-decoration:none;margin-right:1.5rem;font-weight:500}nav a:hover{text-decoration:underline}main{flex:1;padding:2rem;max-width:1200px;margin:0 auto;width:100%}footer{background:#f5f5f5;text-align:center;padding:1rem;margin-top:auto}