body{font-family:sans-serif;max-width:700px;margin:2rem auto;}
textarea{width:100%;height:6rem;margin-top:1rem;}
pre{background:#222;color:#0f0;padding:1rem;overflow-x:auto;}
button{margin-top:1rem;padding:.6rem 1rem;font-size:1rem;}
#viewer{height:300px;border:1px solid #ccc;margin-top:1rem;}
img{max-width:100%;margin-top:1rem;}