html,
body {
  background-color: #fff;
  font-family: "Helvetica", "Arial", "Verdana", sans-serif;
  margin: 0;
  padding: 0;
}

.app-container {
  max-width: 100%;
  overflow: hidden;
}

.header {
  background-color: #369;
  padding: 10px 0;
}

.header > h1 {
  color: #fff;
  font-size: 24px;
  font-weight: 400;
  margin: 0;
  text-align: center;
}

.container {
  background-color: #555;
  display: flex;
  flex-direction: column;
  gap: 1px;
  margin: 24px auto 0;
  padding: 1px;
  text-align: center;
  width: 352px;
}

.row {
  display: flex;
  gap: 1px;
}

.cell {
  background-color: #fff;
  font-size: 20px;
  height: 54px;
  width: 54px;
}

.cell.equals {
  line-height: 52px;
  width: 22px;
}

.cell.blank {
  color: #0b0;
  font-size: 24px;
  font-weight: bold;
  line-height: 54px;
}

.cell.gray {
  background-color: transparent;
}

.cell input {
  height: 50px;
  margin: 2px;
  padding: 0;
  width: 50px;
  border: none;
  font-size: 24px;
  text-align: center;
}

.cell input.add {
  font-size: 32px;
}

.cell input.subtract {
  font-size: 38px;
  height: 45px;
  padding-bottom: 5px;
}

.cell input.divide {
  font-size: 26px;
  font-weight: bold;
}

.equals > .cell {
  height: 22px;
  line-height: 22px;
}

.cell input:not(:focus-visible):placeholder-shown {
  outline: #f90 auto 1px;
}

.solution input {
  -moz-appearance: textfield;
}

.solution input::-webkit-outer-spin-button,
.solution input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.status-bar {
  background-color: #eee;
  height: 10px;
  margin: 5px auto 60px;
  width: 354px;
}

.status-bar.thinking {
  background-color: #369;
}

.status-bar.complete {
  background-color: #0b0;
}

.status-bar.invalid {
  background-color: #911;
}