* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background: #f3f6fb;
  color: #172033;
  font: 16px/1.4 system-ui, sans-serif;
  display: flex;
  justify-content: center;
  padding: 24px 16px;
}

.card {
  width: 390px;
  max-width: 100%;
  background: #fff;
  border-radius: 16px;
  padding: 24px;
  box-shadow: 0 10px 30px rgba(23, 32, 51, 0.08);
}

h1 {
  margin: 0 0 8px;
  font-size: 1.4rem;
}

label {
  display: block;
  margin: 14px 0 6px;
  font-size: 0.85rem;
  font-weight: 600;
}

select,
input,
button {
  width: 100%;
  font: inherit;
  border-radius: 8px;
}

select,
input {
  padding: 10px 12px;
  border: 1px solid #d5dce8;
  background: #fff;
}

button {
  margin-top: 16px;
  padding: 10px 16px;
  border: 0;
  background: #2457d6;
  color: #fff;
  font-weight: 600;
  cursor: pointer;
}

select:focus,
input:focus,
button:focus {
  outline: 2px solid #2457d6;
  outline-offset: 2px;
}

.error {
  min-height: 1.2em;
  margin: 10px 0 0;
  color: #b42318;
  font-size: 0.9rem;
}

.output {
  display: block;
  min-height: 1.4em;
  margin: 0;
  font-family: ui-monospace, "Cascadia Mono", Consolas, monospace;
  font-size: 1.5rem;
  color: #2457d6;
}