body {
  background-color: #f0f4f8;
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.calculator-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px;
}

.scientific-button {
  text-decoration: none;
  background-color: #2a9d8f;
  color: #ffffff;
  padding: 10px 20px;
  border-radius: 10px;
  font-weight: bold;
  transition: background-color 0.2s, transform 0.1s;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
}

.scientific-button:hover {
  background-color: #21877b;
  transform: scale(1.05);
}

.scientific-button:active {
  transform: scale(0.98);
}

.theme-toggle {
  background-color: #f4f6f8;
  color: #495057;
  border: none;
  padding: 10px 20px;
  border-radius: 10px;
  font-weight: bold;
  cursor: pointer;
  transition: background-color 0.2s, transform 0.1s;
  box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 1000;
}

.theme-toggle:hover {
  background-color: #e9ecef;
}

.theme-toggle:active {
  transform: scale(0.98);
}

.calculator {
  background-color: #ffffff;
  border-radius: 15px;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.1);
  padding: 25px;
  max-width: 320px;
  width: 90%;
  border: 1px solid #e0e6ed;
}

.calculator-screen {
  background-color: #2e3549;
  color: #ffffff;
  font-size: 2.5rem;
  height: 60px;
  border: none;
  border-radius: 10px;
  text-align: right;
  padding: 15px 20px;
  margin-bottom: 20px;
  box-sizing: border-box;
  pointer-events: none;
  width: 100%;
}

.calculator-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 15px;
}

button {
  height: 60px;
  font-size: 1.5rem;
  border: none;
  border-radius: 10px;
  cursor: pointer;
  transition: background-color 0.2s, transform 0.1s;
  font-weight: bold;
  color: #495057;
}

button:hover {
  background-color: #e9ecef;
}

button:active {
  transform: scale(0.95);
}

.operator {
  background-color: #f8961e;
  color: #ffffff;
}

.operator:hover {
  background-color: #f5840c;
}

.all-clear,
.clear-last {
  background-color: #e76f51;
  color: #ffffff;
}

.all-clear:hover,
.clear-last:hover {
  background-color: #e55a36;
}

.equal-sign {
  grid-column: span 2;
  background-color: #2a9d8f;
  color: #ffffff;
}

.equal-sign:hover {
  background-color: #21877b;
}

.zero {
  grid-column: span 2;
}

.number-button,
.decimal {
  background-color: #f4f6f8;
}

.number-button:hover,
.decimal:hover {
  background-color: #e9ecef;
}

@media (max-width: 480px) {
  .calculator {
    padding: 15px;
  }

  .calculator-screen {
    font-size: 2rem;
    height: 50px;
    margin-bottom: 15px;
  }

  .calculator-buttons {
    grid-gap: 10px;
  }

  button {
    height: 50px;
    font-size: 1.2rem;
  }
}

.dark-theme {
  background-color: #1a1a1a;
  color: #f0f4f8;
}

.dark-theme .calculator {
  background-color: #2e2e2e;
  border-color: #444444;
}

.dark-theme .calculator-screen {
  background-color: #1c1c1c;
  color: #e0e0e0;
}

.dark-theme button {
  background-color: #404040;
  color: #f0f4f8;
}

.dark-theme .operator {
  background-color: #e76f51;
  color: #ffffff;
}

.dark-theme .operator:hover {
  background-color: #e55a36;
}

.dark-theme .all-clear,
.dark-theme .clear-last {
  background-color: #8338ec;
  color: #ffffff;
}

.dark-theme .all-clear:hover,
.dark-theme .clear-last:hover {
  background-color: #722bb8;
}

.dark-theme .equal-sign {
  background-color: #2a9d8f;
  color: #ffffff;
}

.dark-theme .equal-sign:hover {
  background-color: #21877b;
}

.dark-theme .scientific-button {
  background-color: #2a9d8f;
  color: #ffffff;
}

.dark-theme .scientific-button:hover {
  background-color: #21877b;
}

.dark-theme .scientific {
  background-color: #6a6a6a;
  color: #ffffff;
}

.dark-theme .scientific:hover {
  background-color: #555555;
}

.dark-theme .theme-toggle {
  background-color: #ffffff;
  color: #1a1a1a;
}