style.css

* {
  scrollbar-width: thin;
}

html {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: linear-gradient(to right, #4b6cb7, #182848);
}

.container {
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}

.calculator {
  background: rgba(0, 0, 0, 0.356);
  width: 350px;
  box-shadow: 0 5px 30px -5px rgba(0, 0, 0, 0.6);
}

.calculator-display {
  background: rgba(0, 0, 0, 0.336);
  color: #fff;
  margin: 0;
  display: flex;
  justify-content: flex-end;
  align-items: center;
  border-bottom: 1px solid rgb(106, 110, 148);
}

.calculator-display h1 {
  margin: 0;
  padding: 15px;
  font-size: 2.3rem;
  font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva,
    Verdana, sans-serif;
  font-weight: 100;
  margin-left: 0.4rem;
  margin-right: 0.4rem;
  overflow-x: auto;
}

/* custom scrollbar */
::-webkit-scrollbar {
  width: 5px;
}

::-webkit-scrollbar-track {
  background: #abcfff;
}

::-webkit-scrollbar-thumb {
  background: rgb(32, 61, 124);
  border: 1px solid rgba(0, 0, 0, 0.233);
}

::-webkit-scrollbar-thumb:hover {
  background: rgb(6, 73, 160);
}

/* buttons */
.calculator-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.6rem;
  padding: 0.5rem;
  background: rgb(7, 53, 112);
  margin: 1rem;
}

button {
  margin: 1px;
  min-height: 60px;
  font-size: 1.5rem;
  background: rgb(110, 183, 250);
  font-weight: 100;
  font-family: 'Lucida Sans', 'Lucida Sans Regular', 'Lucida Grande', 'Lucida Sans Unicode', Geneva,
    Verdana, sans-serif;
  cursor: pointer;
  border: none;
  box-shadow: 0 5px 2px 2px rgba(0, 0, 0, 0.6);
}

button:hover {
  filter: brightness(115%);
}

button:active {
  transform: translateY(3px);
  filter: brightness(90%);
  box-shadow: 0 2px 2px 2px rgba(0, 0, 0, 0.6);
}

button:focus {
  outline: none;
}

.operator {
  background: rgb(11, 89, 161);
  color: #fff;
  font-size: 2rem;
}

.clear {
  background: rgb(252, 71, 71);
  color: #fff;
}

.clear:hover {
  filter: brightness(90%);
}

.equal-sign {
  grid-column: -2;
  grid-row: 2 / span 4;
  background: rgb(13, 206, 87);
}

/* media query */
@media screen and (max-width: 600px) {
  .calculator {
    width: 90%;
  }
}