:root {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  color: #172033;
  background: #f4f7fb;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-width: 320px;
}

.calculator {
  width: min(100% - 2rem, 28rem);
  margin: 8vh auto;
  padding: 1.5rem;
  background: #fff;
  border-radius: 0.75rem;
  box-shadow: 0 0.5rem 2rem rgb(23 32 51 / 12%);
}

h1 { margin: 0 0 1.25rem; font-size: 1.5rem; }

h2 { margin: 0; font-size: 1.125rem; }

.operation + .operation {
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid #d9e0eb;
}

.operation form { display: grid; gap: 1rem; margin-top: 0.75rem; }

label { display: grid; gap: 0.4rem; font-weight: 600; }

input, button {
  width: 100%;
  min-height: 2.75rem;
  padding: 0.6rem 0.75rem;
  border-radius: 0.5rem;
  font: inherit;
}

input { border: 1px solid #9aa6b8; }

button {
  border: 0;
  background: #1463d9;
  color: #fff;
  font-weight: 700;
  cursor: pointer;
}

button:hover { background: #0f4eaf; }

output { display: block; margin-top: 1rem; font-size: 1.125rem; font-weight: 700; }