:root {
  /* Light theme */
  --bg-color-light: #f8f9fa;
  --text-color-light: #343a40;
  --btn-bg-light: #ffffff;
  --btn-text-light: #343a40;
  --btn-shadow-light: rgba(0, 0, 0, 0.1);
  --accent-color-light: #7048e8;
  --display-bg-light: #ffffff;
  --number-btn-bg-light: #f8f9fa;
  --operator-btn-bg-light: #e9ecef;
  --equals-btn-bg-light: #7048e8;
  --equals-btn-text-light: #ffffff;
  --function-btn-bg-light: #ffc9c9;
  --function-btn-text-light: #e03131;
  --history-bg-light: #ffffff;
  --history-item-bg-light: #f8f9fa;
  --history-border-light: #e9ecef;

  /* Dark theme */
  --bg-color-dark: #1a1b2e;
  --text-color-dark: #e9ecef;
  --btn-bg-dark: #252a41;
  --btn-text-dark: #e9ecef;
  --btn-shadow-dark: rgba(0, 0, 0, 0.3);
  --accent-color-dark: #7950f2;
  --display-bg-dark: #252a41;
  --number-btn-bg-dark: #2b3151;
  --operator-btn-bg-dark: #343a59;
  --equals-btn-bg-dark: #7950f2;
  --equals-btn-text-dark: #ffffff;
  --function-btn-bg-dark: #4d2626;
  --function-btn-text-dark: #ff8787;
  --history-bg-dark: #252a41;
  --history-item-bg-dark: #2b3151;
  --history-border-dark: #343a59;

  /* Common variables */
  --border-radius-sm: 8px;
  --border-radius-md: 12px;
  --border-radius-lg: 16px;
  --transition-speed: 0.3s;
  --box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
}

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

body {
  font-family: 'Inter', sans-serif;
  background-color: var(--bg-color-light);
  color: var(--text-color-light);
  min-height: 100vh;
  display: flex;
  flex-direction: column; /* Changed to column */
  justify-content: center;
  align-items: center;
  transition: background-color var(--transition-speed), color var(--transition-speed);
  position: relative;
  padding: 1rem;
  overflow-x: hidden; /* Prevent horizontal scrolling */
}


.app-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 1.5rem;
  width: 100%;
  max-width: 450px;
  position: relative; /* Add this to contain absolutely positioned elements */
  overflow-x: hidden; /* Prevent horizontal scrolling */
}


.calculator-container {
  width: 100%;
  background: linear-gradient(145deg, rgba(255, 255, 255, 0.7), rgba(255, 255, 255, 0.3));
  backdrop-filter: blur(10px);
  border-radius: var(--border-radius-lg);
  box-shadow: var(--box-shadow);
  overflow: hidden;
  padding: 1.5rem;
  transition: all var(--transition-speed);
}

/* Header Styles */
.calculator-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
}

.app-title {
  font-family: 'Poppins', sans-serif;
  font-size: 1.8rem;
  font-weight: 700;
  text-align: center;
  color: var(--text-color-light);
  transition: color var(--transition-speed);
}

.app-title span {
  color: var(--accent-color-light);
  transition: color var(--transition-speed);
}

/* Theme Toggle Styles */
.theme-toggle {
  position: relative;
  display: inline-block;
}

.theme-toggle-input {
  opacity: 0;
  width: 0;
  height: 0;
}

.theme-toggle-label {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 60px;
  height: 30px;
  background-color: #e9ecef;
  border-radius: 30px;
  padding: 0 5px;
  cursor: pointer;
  transition: background-color var(--transition-speed);
}

.theme-toggle-label .toggle-slider {
  position: absolute;
  left: 4px;
  width: 22px;
  height: 22px;
  background-color: white;
  border-radius: 50%;
  transition: transform var(--transition-speed);
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.theme-toggle-input:checked + .theme-toggle-label .toggle-slider {
  transform: translateX(30px);
}

.theme-toggle-input:checked + .theme-toggle-label {
  background-color: var(--accent-color-dark);
}

.toggle-icon {
  font-size: 14px;
  z-index: 1;
}

/* Display Styles */
.calculator-display {
  background-color: var(--display-bg-light);
  border-radius: var(--border-radius-md);
  padding: 1rem;
  margin-bottom: 1.5rem;
  box-shadow: inset 0 2px 5px rgba(0, 0, 0, 0.05);
  transition: background-color var(--transition-speed);
}

.previous-operation {
  min-height: 24px;
  font-size: 0.9rem;
  color: #6c757d;
  text-align: right;
  overflow: hidden;
  white-space: nowrap;
  text-overflow: ellipsis;
  margin-bottom: 0.3rem;
}

.calculator-screen {
  width: 100%;
  background: transparent;
  border: none;
  outline: none;
  color: var(--text-color-light);
  font-size: 2.5rem;
  font-weight: 500;
  text-align: right;
  font-family: 'Inter', sans-serif;
  transition: color var(--transition-speed);
  caret-color: var(--accent-color-light);
}

/* Keypad Styles */
.calculator-keypad {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 0.8rem;
}

.btn {
  border: none;
  border-radius: var(--border-radius-sm);
  font-family: 'Inter', sans-serif;
  font-size: 1.2rem;
  font-weight: 500;
  height: 3.5rem;
  cursor: pointer;
  transition: all 0.2s;
  user-select: none;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 5px var(--btn-shadow-light);
}

.btn:active {
  transform: translateY(2px);
  box-shadow: 0 1px 2px var(--btn-shadow-light);
}

.number-btn {
  background-color: var(--number-btn-bg-light);
  color: var(--btn-text-light);
}

.operator-btn {
  background-color: var(--operator-btn-bg-light);
  color: var(--btn-text-light);
  font-size: 1.4rem;
}

.function-btn {
  background-color: var(--function-btn-bg-light);
  color: var(--function-btn-text-light);
}

.equals-btn {
  background-color: var(--equals-btn-bg-light);
  color: var(--equals-btn-text-light);
  font-size: 1.6rem;
}

/* History Button Style */
.history-button {
  background: transparent;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-color-light);
  transition: color var(--transition-speed);
}

.history-button svg {
  width: 24px;
  height: 24px;
}

/* History Panel */
.history-panel {
  position: absolute;
  top: 0;
  right: -100%;
  width: 100%;
  max-width: 450px;
  height: 100%;
  background-color: var(--history-bg-light);
  box-shadow: -5px 0 15px rgba(0, 0, 0, 0.1);
  transition: transform var(--transition-speed); /* Change from right to transform */
  transform: translateX(100%); /* Start off-screen */
  z-index: 10;
  display: flex;
  flex-direction: column;
  border-radius: var(--border-radius-lg) 0 0 var(--border-radius-lg);
}

.history-panel.active {
  right: 0; /* Keep this for compatibility */
  transform: translateX(0); /* Slide in with transform instead */
}

.history-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1.5rem;
  border-bottom: 1px solid var(--history-border-light);
}

.history-header h2 {
  font-family: 'Poppins', sans-serif;
  font-size: 1.5rem;
  font-weight: 600;
}

.history-actions {
  display: flex;
  gap: 0.5rem;
}

.clear-history-btn, .close-history-btn {
  background: transparent;
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  color: var(--accent-color-light);
  font-family: 'Inter', sans-serif;
  font-size: 0.9rem;
  transition: color var(--transition-speed);
}

.close-history-btn svg {
  width: 24px;
  height: 24px;
}

.history-content {
  flex: 1;
  overflow-y: auto;
  padding: 1rem;
}

.history-item {
  background-color: var(--history-item-bg-light);
  border-radius: var(--border-radius-sm);
  padding: 1rem;
  margin-bottom: 0.8rem;
  transition: background-color var(--transition-speed);
}

.history-expression {
  font-size: 1rem;
  margin-bottom: 0.5rem;
  color: #6c757d;
}

.history-result {
  font-size: 1.5rem;
  font-weight: 500;
}

.history-result.negative {
  color: #e03131;
}

.history-result.positive {
  color: #2b8a3e;
}

.history-date {
  font-size: 0.8rem;
  color: #adb5bd;
  margin-top: 0.5rem;
  text-align: right;
}

.empty-history {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100%;
  color: #adb5bd;
  text-align: center;
  padding: 2rem;
}

.empty-history svg {
  width: 64px;
  height: 64px;
  margin-bottom: 1rem;
  opacity: 0.5;
}

/* Orientation Warning */
.orientation-warning {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--bg-color-light);
  z-index: 100;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 2rem;
  text-align: center;
}

.orientation-warning svg {
  width: 64px;
  height: 64px;
  margin-bottom: 1rem;
  color: var(--accent-color-light);
}

/* Footer */
.app-footer {
  text-align: center;
  padding: 1rem 0;
  font-size: 0.9rem;
  color: #6c757d;
  width: 100%;
  position: relative; /* Keep footer in document flow */
  z-index: 1; /* Lower than history panel */
}


.app-footer .heart {
  color: #e03131;
  display: inline-block;
  animation: heartbeat 1.5s infinite;
}

.app-footer a {
  color: var(--accent-color-light);
  text-decoration: none;
  transition: color var(--transition-speed);
}

.app-footer a:hover {
  text-decoration: underline;
}

@keyframes heartbeat {
  0%, 100% { transform: scale(1); }
  50% { transform: scale(1.1); }
}

/* Dark Theme */
body.dark-mode {
  background-color: var(--bg-color-dark);
  color: var(--text-color-dark);
}

body.dark-mode .calculator-container {
  background: linear-gradient(145deg, rgba(37, 42, 65, 0.9), rgba(37, 42, 65, 0.7));
}

body.dark-mode .app-title {
  color: var(--text-color-dark);
}

body.dark-mode .app-title span {
  color: var(--accent-color-dark);
}

body.dark-mode .calculator-display {
  background-color: var(--display-bg-dark);
}

body.dark-mode .calculator-screen {
  color: var(--text-color-dark);
  caret-color: var(--accent-color-dark);
}

body.dark-mode .number-btn {
  background-color: var(--number-btn-bg-dark);
  color: var(--btn-text-dark);
  box-shadow: 0 2px 5px var(--btn-shadow-dark);
}

body.dark-mode .operator-btn {
  background-color: var(--operator-btn-bg-dark);
  color: var(--btn-text-dark);
  box-shadow: 0 2px 5px var(--btn-shadow-dark);
}

body.dark-mode .function-btn {
  background-color: var(--function-btn-bg-dark);
  color: var(--function-btn-text-dark);
  box-shadow: 0 2px 5px var(--btn-shadow-dark);
}

body.dark-mode .equals-btn {
  background-color: var(--equals-btn-bg-dark);
  color: var(--equals-btn-text-dark);
  box-shadow: 0 2px 5px var(--btn-shadow-dark);
}

body.dark-mode .history-button {
  color: var(--text-color-dark);
}

body.dark-mode .history-panel {
  background-color: var(--history-bg-dark);
}

body.dark-mode .history-header {
  border-bottom: 1px solid var(--history-border-dark);
}

body.dark-mode .clear-history-btn, 
body.dark-mode .close-history-btn {
  color: var(--accent-color-dark);
}

body.dark-mode .history-item {
  background-color: var(--history-item-bg-dark);
}

body.dark-mode .orientation-warning {
  background-color: var(--bg-color-dark);
}

body.dark-mode .app-footer a {
  color: var(--accent-color-dark);
}

/* Scientific Calculator Styles */
.header-controls {
  display: flex;
  gap: 0.5rem;
  align-items: center;
}

.scientific-toggle-btn {
  background: linear-gradient(145deg, #667eea, #764ba2);
  border: none;
  border-radius: var(--border-radius-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 0.3rem;
  color: white;
  padding: 0.5rem 0.8rem;
  font-family: 'Inter', sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  transition: all var(--transition-speed);
  box-shadow: 0 2px 8px rgba(102, 126, 234, 0.3);
}

.scientific-toggle-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.scientific-toggle-btn svg {
  width: 16px;
  height: 16px;
}

.scientific-toggle-btn.active {
  background: linear-gradient(145deg, #ff6b6b, #ee5a24);
  box-shadow: 0 2px 8px rgba(255, 107, 107, 0.3);
}

.toggle-text {
  font-size: 0.75rem;
  font-weight: 700;
}

/* Scientific Keypad */
.scientific-keypad {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 0.5rem;
  margin-top: 1rem;
  padding: 1rem;
  background: linear-gradient(145deg, rgba(0, 0, 0, 0.02), rgba(0, 0, 0, 0.05));
  border-radius: var(--border-radius-md);
  border: 2px solid rgba(102, 126, 234, 0.1);
  opacity: 0;
  max-height: 0;
  overflow: hidden;
  transition: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
  transform: translateY(-20px);
}

.scientific-keypad.active {
  opacity: 1;
  max-height: 500px;
  transform: translateY(0);
}

.calculator-container.scientific-mode {
  max-width: 600px;
  transition: max-width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

/* Scientific Button Styles */
.sci-btn {
  height: 2.8rem;
  font-size: 0.85rem;
  font-weight: 500;
  border-radius: var(--border-radius-sm);
  position: relative;
  overflow: hidden;
}

.sci-btn::before {
  content: '';
  position: absolute;
  top: 0;
  left: -100%;
  width: 100%;
  height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
  transition: left 0.5s;
}

.sci-btn:hover::before {
  left: 100%;
}

/* Memory Buttons - Orange/Red Theme */
.memory-btn {
  background: linear-gradient(145deg, #ff6b6b, #ee5a24);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(255, 107, 107, 0.2);
}

.memory-btn:hover {
  background: linear-gradient(145deg, #ff5252, #e53935);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(255, 107, 107, 0.3);
}

/* Angle Button - Purple Theme */
.angle-btn {
  background: linear-gradient(145deg, #667eea, #764ba2);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(102, 126, 234, 0.2);
}

.angle-btn:hover {
  background: linear-gradient(145deg, #5a67d8, #6b46c1);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

.angle-btn.active {
  background: linear-gradient(145deg, #4c51bf, #553c9a);
}

/* Trigonometric Buttons - Blue Theme */
.trig-btn {
  background: linear-gradient(145deg, #4299e1, #3182ce);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(66, 153, 225, 0.2);
}

.trig-btn:hover {
  background: linear-gradient(145deg, #3182ce, #2c5282);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(66, 153, 225, 0.3);
}

/* Logarithmic Buttons - Green Theme */
.log-btn {
  background: linear-gradient(145deg, #48bb78, #38a169);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(72, 187, 120, 0.2);
}

.log-btn:hover {
  background: linear-gradient(145deg, #38a169, #2f855a);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(72, 187, 120, 0.3);
}

/* Scientific Function Buttons - Enhanced */
.scientific-keypad .function-btn {
  background: linear-gradient(145deg, #a78bfa, #8b5cf6);
  color: white;
  font-weight: 600;
  box-shadow: 0 2px 8px rgba(167, 139, 250, 0.2);
}

.scientific-keypad .function-btn:hover {
  background: linear-gradient(145deg, #8b5cf6, #7c3aed);
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(167, 139, 250, 0.3);
}

/* Casio-Style LCD Display Enhancement */
.calculator-container.scientific-mode .calculator-display {
  background: linear-gradient(145deg, #1a202c, #2d3748);
  color: #e2e8f0;
  border: 3px solid #4a5568;
  position: relative;
}

.calculator-container.scientific-mode .calculator-display::before {
  content: 'CASIO';
  position: absolute;
  top: 0.5rem;
  left: 1rem;
  font-size: 0.7rem;
  font-weight: 700;
  color: #a0aec0;
  opacity: 0.7;
}

.calculator-container.scientific-mode .calculator-screen {
  color: #00ff41;
  text-shadow: 0 0 10px rgba(0, 255, 65, 0.5);
  font-family: 'Courier New', monospace;
  background: rgba(0, 0, 0, 0.3);
  border-radius: 4px;
  padding: 0.5rem;
}

/* Dark Mode Scientific Styles */
body.dark-mode .scientific-keypad {
  background: linear-gradient(145deg, rgba(255, 255, 255, 0.02), rgba(255, 255, 255, 0.05));
  border-color: rgba(121, 80, 242, 0.2);
}

body.dark-mode .scientific-toggle-btn {
  background: linear-gradient(145deg, #7950f2, #6c5ce7);
  box-shadow: 0 2px 8px rgba(121, 80, 242, 0.3);
}

body.dark-mode .scientific-toggle-btn.active {
  background: linear-gradient(145deg, #fd79a8, #e84393);
}

/* Animation for mode switching */
@keyframes expandScientific {
  from {
    opacity: 0;
    max-height: 0;
    transform: translateY(-20px);
  }
  to {
    opacity: 1;
    max-height: 500px;
    transform: translateY(0);
  }
}

@keyframes collapseScientific {
  from {
    opacity: 1;
    max-height: 500px;
    transform: translateY(0);
  }
  to {
    opacity: 0;
    max-height: 0;
    transform: translateY(-20px);
  }
}

.scientific-keypad.expanding {
  animation: expandScientific 0.5s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

.scientific-keypad.collapsing {
  animation: collapseScientific 0.5s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

/* Memory indicator */
.memory-indicator {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: linear-gradient(145deg, #ff6b6b, #ee5a24);
  color: white;
  padding: 0.2rem 0.5rem;
  border-radius: 12px;
  font-size: 0.7rem;
  font-weight: 600;
  opacity: 0;
  transform: scale(0);
  transition: all var(--transition-speed);
}

.memory-indicator.active {
  opacity: 1;
  transform: scale(1);
}

/* Responsive adjustments for scientific mode */
@media (max-width: 768px) {
  .calculator-container.scientific-mode {
    max-width: 100%;
  }
  
  .scientific-keypad {
    grid-template-columns: repeat(3, 1fr);
    gap: 0.4rem;
  }
  
  .sci-btn {
    height: 2.5rem;
    font-size: 0.75rem;
  }
}

@media (max-width: 480px) {
  .scientific-keypad {
    padding: 0.8rem;
  }
  
  .sci-btn {
    height: 2.2rem;
    font-size: 0.7rem;
  }
  
  .header-controls {
    gap: 0.3rem;
  }
  
  .scientific-toggle-btn {
    padding: 0.4rem 0.6rem;
    font-size: 0.7rem;
  }
}