body{font-family:Arial,sans-serif;background:#f6f6f6;margin:0;padding:0}
nav{background:#000;color:#fff;padding:1rem}
nav a{color:#fff;text-decoration:none;font-size:1.2rem}
main{max-width:800px;margin:auto;padding:2rem}
textarea{width:100%;height:200px;padding:.5rem;margin:1rem 0}
button{padding:.5rem 1rem;font-size:1rem;margin:auto;display:block}
section.hidden{display:none}
section{background:#fff;padding:1rem;margin:1rem 0}
#sentences p{background:#ffe0e0;padding:.5rem;margin:.5rem 0}