style.css

* {
  margin: 0;
  /*border: 1px solid red;*/
  box-sizing: border-box;
}
html {
  display: flex;
  height: 100vh;
  justify-content: center;
  align-items: center;
  background-color: #c6c6c6;
}
#calc-background {
  height: 450px;
  width: 300px;
  border-radius: 15px;
  background-color: black;
  display: flex;
  flex-wrap: wrap;
}
#calc-screen {
  position: relative;
  margin: 0 auto;
  margin-top: 15px;
  height: 70px;
  width: 270px;
  border-radius: 15px;
  background-color: #2b3025;
}
#display {
  color: white;
  font-family: arial;
  position: absolute;
  top: 35px;
  right: 10px;
  font-size: 30px;
  z-index: 1;
}
#calc-buttons {
  position: relative;
  height: 340px;
  width: 270px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  align-content: flex-start;
}
.lg-buttons {
  height: 60px;
  width: 130px;
  border-radius: 50px;
  display: flex;
}
.lg-button-vert {
  height: 130px;
  width: 60px;
  border-radius: 50px;
  display: flex;
}
.sm-buttons {
  height: 60px;
  width: 60px;
  border-radius: 50%;
  display: flex;
}
.grey-buttons {
  background-color: #c6c6c6;
}
.orange-buttons {
  background-color: #ed9700;
}
.margin-left {
  margin-left: 10px;
}
.margin-top {
  margin-top: 10px;
}
#zero {
  position: absolute;
  top: 280px;
}
#decimal {
  position: absolute;
  top: 280px;
  left: 130px;
}
.btn.lg-buttons p{
  font-family: arial;
  font-weight: bold;
  font-size: 25px;
  margin: auto;
}
.btn.sm-buttons p{
  font-family: arial;
  font-weight: bold;
  font-size: 25px;
  margin: auto;
}
.btn.lg-button-vert p{
  font-family: arial;
  font-weight: bold;
  font-size: 25px;
  margin: auto;
}
p {
  user-select: none;
}
.btn:hover {
  border: 3px solid white;
  color: white;
}