html {
  box-sizing: border-box;
}
*,
*:before,
*:after {
  box-sizing: inherit;
}

body {
  margin: 0;
  background: #000;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  font-family: -apple-system, BlinkMacSystemFont, sans-serif;
}

.wrapper {
  width: 400px;
  background: #000;
  border-radius: 20px;
  overflow: hidden;
}

/* Screen */
.calculator-screen {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: flex-end;
  padding: 20px;
  height: 120px;
}

.history {
  color: rgba(255, 255, 255, 0.6);
  font-size: 18px;
}

.screen {
  color: white;
  font-size: 48px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
/* Buttons container */
.calculator-buttons {
  display: flex;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  width: 25%;
  height: 80px;
  border: 1px solid #000;
  font-size: 24px;
  color: black;
  display: flex;
  justify-content: center;
  align-items: center;
}

/* Special styles */
.btn.operator {
  background: orange;
}

.btn.function {
  background: #a5a5a5;
  color: black;
}

/* Zero button spans two columns */
.btn.zero {
  width: 50%;
  justify-content: flex-start;
  padding-left: 30px;
}

/* Button press effect */
.btn:active {
  filter: brightness(1.2);
}

.btn {
  transition: all 0.15s ease;
  cursor: pointer;
}

.btn:hover {
  filter: brightness(1.3);
}

.btn:active {
  transform: scale(0.95);
  filter: brightness(1.1);
}