styles.css

@keyframes lightup {
  0% {
    filter: saturate(90%);
  }
  50% {
    filter: saturate(650%);
  }
  100% {
    filter: saturate(140%);
  }
}
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
:root {
  --bg: rgb(90, 90, 90);
}
body {
  background: var(--bg);
}

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

.calc {
  background: rgb(232, 232, 232);
  height: clamp(320px, 35vw, 80vh);
  width: clamp(350px, 38vw, 40vw);
  border-radius: 3vw;
  padding: 1.85rem;
  border: 1px solid rgb(0, 0, 0, 0);
  outline: none;
  box-shadow: 1.252vw 1.252vw 2vw rgb(0, 0, 0, 0.56);
  display: flex;
  flex-direction: column;
  justify-content: space-evenly;
}

.operands {
  display: flex;
  flex-direction: column;
  width: 100%;
  height: 12vw;
  justify-content: space-between;
}

.ans {
  display: flex;
  width: 100%;
  flex-direction: column;
}

.box {
  outline: none;
  background: none;
  box-shadow: inset -2px -3px 5px rgb(0, 0, 0, 0.3), -4px -6px 5px white;
  border: none;
  padding: 10px 30px;
  font-size: 3vw;
  font-family: arial;
  font-weight: 800;
  border-radius: 50vw;
  margin: 0.8vw 0;
}

input[type="number"] {
  -moz-appearance: textfield;
}

input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
}
input[type="number"]:focus {
  box-shadow: inset 3px 2px 4px rgb(0, 0, 0, 0.3), 3px 2px 4px white;
}

#res {
  pointer-events: none;
  /* text-shadow: 0 0 5px rgb(0, 124, 0); */
  color: green;
  font-weight: 1000;
  box-shadow: inset 3px 2px 4px rgb(0, 0, 0, 0.3), 3px 2px 4px white;
}

.operators {
  display: flex;
  justify-content: space-between;
  margin: 2.6vw 0 0.5vw 0;
}

.operator {
  font-size: 4.5vw;
  font-family: sans-serif;
  font-weight: 700;
  border: none;
  outline: none;
  border-radius: 50%;
  width: 5.7vw;
  height: 5.7vw;
  background: radial-gradient(rgb(33, 90, 128), rgb(36, 36, 36));
  color: white;
  cursor: pointer;
}

.operator:active {
  background: radial-gradient(rgb(12, 155, 250), rgb(0, 71, 79));
  transition: 0.5s background ease-in-out;
}

#clear:active {
  background: radial-gradient(rgb(255, 0, 0), rgb(221, 2, 2));
}

#plus {
  animation: lightup 0.6s both ease-in-out 1;
  animation-delay: 1s;
}
#minus {
  animation: lightup 0.6s both ease-in-out 1;
  animation-delay: 1.2s;
  font-family: sans-serif;
}
#multiply {
  animation: lightup 0.6s both ease-in-out 1;
  animation-delay: 1.6s;
}
#divide {
  animation: lightup 0.6s both ease-in-out 1;
  animation-delay: 2s;
}

#clear {
  margin-left: 33px;
  background: radial-gradient(rgb(155, 40, 40), rgb(107, 33, 33));
  animation: lightup 0.6s both ease-in-out 1;
  animation-delay: 2.4s;
}
@media screen and (max-width: 500px) {
  .calc {
    height: clamp(300px, 60vh, 800px);
    width: clamp(270px, 85vw, 90vw);
    border-radius: 5.25vw;
    padding: 1.1975rem;
  }

  .operands {
    display: flex;
    flex-direction: column;
    width: 100%;
    height: fit-content;
    justify-content: space-between;
  }

  .ans {
    display: flex;
    width: 100%;
    flex-direction: column;
  }

  .box {
    outline: none;
    background: none;
    box-shadow: inset -2px -3px 5px rgb(0, 0, 0, 0.3), -4px -6px 5px white;
    border: none;
    padding: 10px 30px;
    font-size: 35px;
    font-weight: 1000;
    border-radius: 50vw;
    margin: 12px 0;
  }

  input[type="number"]:focus {
    box-shadow: inset 3px 2px 4px rgb(0, 0, 0, 0.3), 3px 2px 4px white;
  }

  .operators {
    display: flex;
    justify-content: space-between;
    margin: 0 5px;
  }

  .operator {
    font-size: 35px;
    font-weight: 500;
    width: 50px;
    height: 50px;
    border: none;
    outline: none;
    border-radius: 50%;
    background: radial-gradient(rgb(33, 90, 128), rgb(36, 36, 36));
    color: white;
    cursor: pointer;
  }

  #minus,
  #clear {
    font-size: 30px;
    font-weight: 700;
    margin: 0;
  }
}