* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  text-align: center;
  padding-inline: 1rem;
  font-family: ui-sans-serif, system-ui, sans-serif, "Apple Color Emoji",
    "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
  min-height: 100vh;
  background: #f9fafb;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

main {
  display: flex;
  flex-direction: column;
  row-gap: 1.25rem;
  background: transparent;
  width: max-content;
  max-width: 100%;
  padding: 1.25rem;
  border-radius: 0.5rem;
}

header {
  width: 100%;
  text-align: left;
  outline: 1px solid #9ca3af;
  border-radius: 0.25rem;
  padding: 0.5rem;
  user-select: none;
}

label {
  display: block;
  font-size: 0.875rem;
  line-height: 1.25rem;
  font-weight: 500;
  color: #9ca3af;
}

input {
  text-align: right;
  width: 100%;
  font-size: 1.25rem;
  line-height: 1.75rem;
  margin-top: 1.25rem;
  border: none;
  color: #111827;
  background: transparent;
  cursor: not-allowed;
}
input:focus {
  outline: none;
}

section {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.5rem;
}

button {
  font-size: 1.125rem;
  line-height: 1.75rem;
  border: 1px solid #e5e7eb;
  border-radius: 0.25rem;
  cursor: pointer;
  box-shadow: rgba(14, 63, 126, 0.06) 0px 0px 0px 1px, rgba(42, 51, 70, 0.03) 0px 1px 1px -0.5px, rgba(42, 51, 70, 0.04) 0px 2px 2px -1px, rgba(42, 51, 70, 0.04) 0px 3px 3px -1.5px, rgba(42, 51, 70, 0.03) 0px 5px 5px -2.5px, rgba(42, 51, 70, 0.03) 0px 10px 10px -5px, rgba(42, 51, 70, 0.03) 0px 24px 24px -8px;
}
button:not(:last-child) {
  width: 60px;
  height: 60px;
  color: #111827;
  background: #f3f4f6;
}

.operator {
  color: #3b82f6 !important;
}

.operator.calculate {
  grid-column: span 2 / span 2;
  color: #f3f4f6 !important;
  background: #3b82f6;
}