body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: #f9fafb;
  color: #222;
  margin: 0;
  padding: 20px;
}

.container {
  max-width: 460px;
  margin: 2rem auto;
  background: #fff;
  padding: 25px 30px;
  box-shadow: 0 0 12px rgba(0,0,0,0.1);
  border-radius: 8px;
  text-align: center;
}

h1 {
  font-weight: 700;
  margin-bottom: 12px;
  font-size: 1.8rem;
}

p {
  margin-bottom: 20px;
  color: #555;
  font-size: 1rem;
}

.converter {
  display: flex;
  align-items: center;
  gap: 10px;
  justify-content: center;
  flex-wrap: nowrap;
}

input[type="number"] {
  width: 120px;
  padding: 10px 12px;
  border: 1px solid #ccc;
  border-radius: 6px;
  font-size: 1rem;
  outline-offset: 2px;
  outline-color: #6c63ff;
}

input[readonly] {
  background-color: #f0f0f0;
  cursor: default;
}

select {
  padding: 10px 12px;
  border-radius: 6px;
  border: 1px solid #ccc;
  font-size: 1rem;
  background-color: #fff;
  cursor: pointer;
}

button#swapBtn {
  background-color: #6c63ff;
  color: #fff;
  border: none;
  font-size: 1.6rem;
  padding: 8px 12px;
  border-radius: 50%;
  cursor: pointer;
  transition: background-color 0.3s ease;
  user-select: none;
}

button#swapBtn:hover {
  background-color: #574fd6;
}

@media (max-width: 480px) {
  .converter {
    flex-wrap: wrap;
    gap: 12px;
  }
  
  input[type="number"], select {
    width: 100%;
  }
  
  button#swapBtn {
    flex-grow: 1;
  }
}