calculator.css

:root {
  --dark-color:  #33333d;
  --accent-green: #04b97f;
  --accent-red: #c64e4e;
  --light-color: whitesmoke;
}

* {
  font-size: 22px;
  font-family: 'Commissioner', sans-serif;
  color: var(--light-color);
  overflow: hidden;
}

body {
  background-color: var(--dark-color);
}

#page {
  position: fixed;
  top: 0px;
  bottom: 0px;
  left: 0px;
  right: 0px;
  display: flex;
  align-items: center;
  justify-content: center;
}

#screen {
  text-align: right;
  overflow: hidden;
  max-width: 30px;
  max-height: 30px;
}

table, th, td {
  border: 2px solid var(--accent-green);
  border-radius: 10px;
  padding: 5px;
  font-weight: bold;
  overflow: hidden;
}

table {
  border-spacing: 5px;
}

th, td {
  padding: 15px;
}

th {
  width: 30px;
  height: 30px;
  transition: 0.3s;
}

th:hover {
  cursor: pointer;
  background-color: var(--accent-green);
}

td {
  letter-spacing: 2px;
}

.icon {
  display: flex;
  align-items: center;
  justify-content: center;
  border: 2px solid var(--accent-red);
  transition: 0.3s;
}

.icon:hover {
  background-color: var(--accent-red);
}