body {background:#111; color:#eee; font-family:system-ui, sans-serif; padding:10px; margin:0;}
h1,h2{text-align:center;}
button {
  background:#4caf79;
  border:none;
  padding:8px 12px;
  margin:3px;
  font-size:16px;
  cursor:pointer;
  border-radius:6px;
  color:#fff;
  transition:0.2s;
}
button:hover {background:#399166;}
.container {max-width:500px; margin:auto;}
.card {background:#1b1b1b; padding:16px; margin:12px 0; border-radius:8px;}
.hidden {display:none;}
input {padding:6px; font-size:16px; width:60px; margin-right:4px;}
.correct{color:#2ecc71; font-weight:bold;}
.wrong{color:#e74c3c; font-weight:bold;}