@import url("https://fonts.googleapis.com/css2?family=Roboto+Mono:wght@400;500&family=Roboto:wght@400;500&display=swap");

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  background: #111118;
  background-image:
    radial-gradient(
      ellipse at 20% 50%,
      rgba(80, 60, 140, 0.15) 0%,
      transparent 60%
    ),
    radial-gradient(
      ellipse at 80% 20%,
      rgba(40, 80, 160, 0.1) 0%,
      transparent 50%
    );
  font-family: "Roboto", sans-serif;
  color: white;
}

header {
  text-align: center;
  padding: 24px 20px 16px;
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  opacity: 0.35;
}

main {
  flex: 1;
  display: flex;
  justify-content: center;
  align-items: center;
}

#calculator {
  background: #1c1c28;
  padding: 24px;
  border-radius: 20px;
  width: 340px;
  box-shadow:
    0 0 0 1px rgba(255, 255, 255, 0.06),
    0 20px 60px rgba(0, 0, 0, 0.6),
    0 4px 12px rgba(0, 0, 0, 0.4);
}

#display {
  width: 100%;
  height: 76px;
  margin-bottom: 18px;
  border: none;
  border-radius: 12px;
  background: #0d0d14;
  color: #e8ffe8;
  font-family: "Roboto Mono", monospace;
  font-size: 2.2rem;
  text-align: right;
  padding: 10px 16px;
  box-shadow:
    inset 0 2px 6px rgba(0, 0, 0, 0.5),
    0 0 0 1px rgba(255, 255, 255, 0.04);
  caret-color: transparent;
  letter-spacing: 0.02em;
}

#keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

button {
  padding: 18px;
  font-family: "Roboto Mono", monospace;
  font-size: 1.2rem;
  border: none;
  border-radius: 12px;
  background: #262636;
  color: rgba(255, 255, 255, 0.85);
  cursor: pointer;
  transition:
    background 0.1s ease,
    transform 0.1s ease,
    box-shadow 0.1s ease;
  box-shadow:
    0 2px 4px rgba(0, 0, 0, 0.3),
    0 0 0 1px rgba(255, 255, 255, 0.04);
  position: relative;
}

button:hover {
  background: #31314a;
  color: #fff;
}

button:active {
  transform: scale(0.94);
  box-shadow: 0 1px 2px rgba(0, 0, 0, 0.3);
}

button[onclick*="setOperator"] {
  background: #7c4dff;
  color: #fff;
  box-shadow:
    0 2px 8px rgba(124, 77, 255, 0.35),
    0 0 0 1px rgba(255, 255, 255, 0.06);
}

button[onclick*="setOperator"]:hover {
  background: #9166ff;
  box-shadow: 0 4px 12px rgba(124, 77, 255, 0.45);
}

button[onclick="calculate()"] {
  background: #00c06b;
  color: #fff;
  box-shadow:
    0 2px 8px rgba(0, 192, 107, 0.3),
    0 0 0 1px rgba(255, 255, 255, 0.06);
}

button[onclick="calculate()"]:hover {
  background: #00d97a;
  box-shadow: 0 4px 12px rgba(0, 192, 107, 0.45);
}

button[onclick="clearDisplay()"] {
  background: #e03e52;
  color: #fff;
  box-shadow:
    0 2px 8px rgba(224, 62, 82, 0.3),
    0 0 0 1px rgba(255, 255, 255, 0.06);
}

button[onclick="clearDisplay()"]:hover {
  background: #f05060;
  box-shadow: 0 4px 12px rgba(224, 62, 82, 0.45);
}

.backspace {
  background: #2e2e42;
  color: rgba(255, 255, 255, 0.7);
}

.backspace:hover {
  background: #3a3a52;
  color: #fff;
}

/* #keys button:nth-child(1),
#keys button:nth-child(2) {
  grid-column: span 2;
} */

footer {
  text-align: center;
  padding: 14px;
  font-size: 0.75rem;
  letter-spacing: 0.03em;
  opacity: 0.25;
}

.shake {
  animation: shake 0.3s ease;
}

@keyframes shake {
  0% {
    transform: translateX(0);
  }
  20% {
    transform: translateX(-7px);
  }
  40% {
    transform: translateX(7px);
  }
  60% {
    transform: translateX(-5px);
  }
  80% {
    transform: translateX(5px);
  }
  100% {
    transform: translateX(0);
  }
}

@media (max-width: 500px) {
  #calculator {
    width: 90vw;
    padding: 20px;
  }

  #display {
    font-size: 1.9rem;
    height: 68px;
  }

  button {
    padding: 15px;
    font-size: 1.1rem;
  }

  #keys {
    gap: 8px;
  }
}

@media (max-width: 360px) {
  #calculator {
    width: 95vw;
    padding: 14px;
  }

  #display {
    font-size: 1.6rem;
    height: 60px;
  }

  button {
    padding: 12px;
    font-size: 1rem;
  }

  #keys {
    gap: 6px;
  }
}