styles.css

@import url("https://fonts.googleapis.com/css2?family=Noto+Sans:ital,wght@0,100..900;1,100..900&family=Roboto:ital,wght@0,100;0,300;0,400;0,500;0,700;0,900;1,100;1,300;1,400;1,500;1,700;1,900&display=swap");

/* ================================================== */
/* BASIC SETUP */
/* ================================================== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

li {
  list-style-type: none;
}

body {
  font-family: "Roboto", sans-serif;
  line-height: 1.6;
  background-color: #f1f1f1;
}

.container {
  max-width: 1100px;
  margin: 0 auto;
  overflow: auto;
  padding: 0 40px;
}

.container .title {
  text-align: center;
}

/* === Calculator === */
.calculator {
  width: 400px;
  height: 650px;
  background-color: #000;
  margin: 0 auto;
  border-radius: 20px;
  padding: 20px;
  margin-top: 40px;
}

.calculator .display {
  overflow-x: scroll;
}

.calculator .display h1 {
  color: #fff;
  text-align: right;
  font-size: 52px;
}

.control-keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;

  margin-top: 50px;
}

.control-keys .btn {
  width: 78px;
  height: 78px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 26px;
  font-weight: bold;

  display: flex;
  justify-content: center;
  align-items: center;
}

.control-keys .btn-func {
  background-color: #A5A5A5;
  color: #000;
}

.control-keys .btn-func:focus {
  background-color: #A5A5A5;
  transition: all 1s;
}

.control-keys .btn-func:active {
  background-color: #BFBFBF;
  transition: background-color 0.1s;
}

.control-keys .btn-operator,
.control-keys .btn-run {
  background-color: #FF9500;
  color: #fff;
}

.control-keys .btn-operator:focus,
.control-keys .btn-run:focus {
  background-color: #FF9500;
  transition: all 1s;
}

.control-keys .btn-operator:active,
.control-keys .btn-run:active {
  background-color: #FFA64D;
  transition: background-color 0.1s;
}

.control-keys .btn-num {
  background-color: #4B4B4B;
  color: #fff;
}

.control-keys .btn-num:focus {
  background-color: #4B4B4B;
  transition: all 1s;
}

.control-keys .btn-num:active {
  background-color: #666666;
  transition: background-color 0.1s;
}

.control-keys .btn-zero {
  grid-column: 1 / 3;
  width: auto;
  border-radius: 50px;
}