*{margin:0;padding:0;box-sizing:border-box}body{display:flex;justify-content:center;align-items:center;min-height:100vh;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:#f5f5f5;color:#333}.card{background:#fff;padding:2rem;border-radius:12px;box-shadow:0 2px 8px #0000001a;text-align:center;max-width:400px;width:100%;margin:1rem}.card h2{margin-bottom:1rem}.card p{margin-bottom:1.5rem;color:#666}.btn{background:#08c;color:#fff;border:none;padding:12px 24px;border-radius:8px;font-size:16px;cursor:pointer;margin:8px;transition:opacity .2s}.btn:hover{opacity:.9}.btn:disabled{opacity:.5;cursor:not-allowed}.error{color:#e74c3c;margin-top:1rem}