body{font-family:Arial,sans-serif;margin:0;padding:0;display:flex;flex-direction:column;align-items:center;justify-content:flex-start;min-height:100vh;background-color:#f5f5f5}header{background:#333;color:#fff;width:100%;padding:1rem 0;text-align:center}nav ul{list-style:none;display:flex;justify-content:center;gap:2rem;padding:0;margin:0}nav a{color:#fff;text-decoration:none;font-weight:700;transition:color .3s}nav a:hover{color:#fc0}main{padding:2rem;text-align:center;width:90%;max-width:1000px}@media screen and (max-width:768px){nav ul{flex-direction:column;gap:1rem}main{padding:1rem}}@media screen and (max-width:480px){nav a{font-size:1rem}main{font-size:.9rem}}