body {
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: #f4f6f8;
  margin: 0;
  padding: 40px;
  color: #333;
}

h2 {
  margin-top: 0;
  font-size: 28px;
  font-weight: 600;
  color: #222;
  text-align: center;
}

/* Kontejner pro tlačítka */
.controls {
  display: flex;
  justify-content: center;
  gap: 12px;
  margin-top: 10px;
  margin-bottom: 20px;
}

button {
  background: #0078d4;
  color: white;
  border: none;
  padding: 12px 22px;
  font-size: 16px;
  border-radius: 8px;
  cursor: pointer;
  transition: 0.2s;
}

button:hover {
  background: #005fa3;
}

#gridContainer {
  margin-top: 25px;
  display: flex;
  justify-content: center;
}

.grid {
  background: white;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
  display: grid;
  gap: 8px;
}

.grid input {
  width: 60px;
  height: 60px;
  font-size: 22px;
  text-align: center;
  border: 2px solid #d0d7de;
  border-radius: 8px;
  transition: 0.2s;
}

.grid input:focus {
  border-color: #0078d4;
  box-shadow: 0 0 0 3px rgba(0,120,212,0.2);
  outline: none;
}

.grid input:disabled {
  background: #e9eef3;
  color: #555;
  font-weight: bold;
}

#result {
  margin-top: 20px;
  font-size: 20px;
  font-weight: 600;
  text-align: center;
}

.ok {
  color: #0a8a0a;
}

.fail {
  color: #c62828;
}