style.css

.calculator {
  width: fit-content;
  margin: 4em auto;
  border: 1px solid black;
  padding: 1em;
  box-shadow: 0.3em 0.3em 0.5em #8e8c8c;
  border-radius: 0.8em;
}
button {
  width: 5em;
  height: 4em;
  margin: 0.1em;
  font-size: 1.1rem;
  cursor: pointer;
  outline: none;
  border-radius: 1em;
}
.row {
  display: flex;
}
#equal,
#clear {
  width: 10.2em;
  height: 4em;
}
p {
  text-align: right;
  background-color: #8e8c8c;
  padding: 1em;
  color: white;
  font-size: 2rem;
  border-radius: 0.8em;
  border: 1px solid #5c5c5c;
  pointer-events: none;
}

/* color buttons */
.number,
#decimal {
  background-color: #c2c2c2;
}
#delete,
#clear {
  background-color: #f55252;
}
.operations {
  background-color: #ffa500;
}
.selected {
  background-color: #b38531;
  border-color: #886421;
}
#equal {
  background-color: #7fb829;
}