:root{
  --accent-color: #b0c636;
  --body-bg-color: linear-gradient(#4f575f, #212529);
  --box-shadow: -3px -3px 4px #cacfd245, 3px 3px 4px #000000;
  --box-shadow-hover: 1px -1px 4px #000000, -1px 1px 4px #cacfd245;
  --box-shadow-inner: 3px -3px 4px #000000, -3px 3px 4px #cacfd245;
  --main-bg-color: #1d2f34;
  --main-color: #ffffff;
}

* {
  font-family: sans-serif;
  margin: 0;
  padding: 0;
}

*, *::after, *::before {
  box-sizing: border-box;
  transition: all 0.35s ease;
}

.body {
  align-items: center;
  background: var(--body-bg-color);
  display: flex;
  height: 100vh;
  justify-content: center;
}

.calculator {
  background-color: var(--main-bg-color);
  border-radius: 1.875em;
  box-shadow: var(--box-shadow);
  height: 550px;
  padding: 15px 10px 10px;
  position: relative;
  width: 300px;
}

.keyboard {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(5, 80px);
  height: 100%;
}

.key {
  align-items: center;
  align-self: center;
  border-radius: 50%;
  background-color: var(--main-bg-color);
  box-shadow: var(--box-shadow);
  color: var(--main-color);
  cursor: pointer;
  display: flex;
  font-size: 20px;
  font-weight: 900;
  height: 60px;
  justify-content: center;
  justify-self: center;
  width: 60px;
}

.key:hover {
  box-shadow: var(--box-shadow-hover);
  transform: scale(0.96);
}

.key:active {
  box-shadow: var(--box-shadow-inner);
  transform: scale(0.92);
}


.operation {
  font-size: 15px;
  color: var(--main-color);
  margin-top: 10px;
  min-height: 18px;
}

.result {
  display: flex;
  flex-direction: column;
  justify-content: flex-end;
}

.screen {
  display: block;
  padding: 10px 10px 30px;
  position: relative;
  text-align: right;
}

.screen::after {
  bottom: 15px;
  color: var(--main-color);
  content: '';
  font-size: 50px;
  font-weight: 100;
  left: 10px;
  position: absolute;
}
.total {
  color: var(--accent-color);
  font-size: 45px;
}