.back-btn,button{padding:10px 20px;color:#fff;cursor:pointer;transition:background-color .3s,transform .2s ease-in-out}*{margin:0;padding:0;box-sizing:border-box;font-family:Arial,sans-serif}body{background:url('../img/background.jpeg') center center/cover no-repeat fixed;display:flex;flex-direction:column;align-items:center;height:100vh}.back-btn{position:fixed;bottom:20px;left:20px;background-color:#ff5733;border:none;border-radius:5px;font-size:1.2rem;box-shadow:0 4px 6px rgba(0,0,0,.2)}.back-btn:hover{background-color:#c0392b;transform:scale(1.1)}.back-btn:active{background-color:#e74c3c;transform:scale(.98)}.content{background:rgba(255,255,255,.9);padding:20px;border-radius:10px;box-shadow:0 4px 8px rgba(0,0,0,.2);margin-top:50px;display:flex;flex-direction:column;align-items:center;max-width:400px;width:100%}h2{margin:15px 0;font-size:1.5rem}input{padding:10px;margin:10px 0;border:2px solid teal;border-radius:5px;font-size:1rem;width:100%;max-width:300px}#changeResult,button{margin-top:20px;font-size:1.2rem}button{background-color:#32cd32;border:none;border-radius:5px}button:hover{background-color:#28a745;transform:scale(1.1)}button:active{background-color:#218838;transform:scale(.98)}.hidden{display:none}