/* Custom Properties */
:root {
    --primary-color: #3498db;
    --shadow-light: 0 4px 20px rgba(0, 0, 0, 0.1);
    --shadow-dark: 0 4px 20px rgba(0, 0, 0, 0.3);
  }
  
  body {
    font-family: 'Segoe UI', Arial, sans-serif;
    padding: 40px;
    margin: 0;
    color: #2c3e50;
    background: linear-gradient(
        -45deg,
        #ff6b6b,  /* Red */
        #ffa502,  /* Orange */
        #f9ca24,  /* Yellow */
        #96c93d,  /* Green */
        #4ecdc4,  /* Teal */
        #45b7d1,  /* Blue */
        #8e44ad,  /* Purple */
        #d81e5b,  /* Pink */
        #ff6b6b   /* Red again for smooth loop */
    );
    background-size: 1000% 1000%;
    animation: fadeIn 0.5s ease-in-out, gradientShift 15s ease infinite;
}

body.dark {
    color: #e0e0e0;
    background: linear-gradient(
        -45deg,
        #2d1b4e,  /* Deep Purple */
        #5e2d79,  /* Purple */
        #8a307f,  /* Magenta */
        #d81e5b,  /* Pink */
        #c0392b,  /* Dark Red */
        #2980b9,  /* Dark Blue */
        #16a085,  /* Teal */
        #27ae60,  /* Green */
        #2d1b4e   /* Deep Purple again for smooth loop */
    );
    background-size: 1000% 1000%;
    animation: fadeIn 0.5s ease-in-out, gradientShift 15s ease infinite;
}

@media (prefers-reduced-motion: reduce) {
    body, body.dark {
        animation: fadeIn 0.5s ease-in-out;
        background-size: 100% 100%;
    }
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes gradientShift {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; } /* Loop back smoothly */
}

  .container {
    max-width: 800px;
    margin: 0 auto;
    box-shadow: var(--shadow-light);
    border-radius: 12px;
    overflow: hidden;
  }
  
  /* Headings */
  h2, h3 {
    color: #2c3e50;
    font-weight: 600;
    margin-bottom: 30px;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.1);
  }
  body.dark h2, body.dark h3 {
    color: #ecf0f1;
  }
  
  /* Calendar Popup */
  .calendar-popup {
    display: none;
    position: absolute;
    background: white;
    border: 1px solid #e0e0e0;
    padding: 15px;
    box-shadow: var(--shadow-light);
    z-index: 1000;
    border-radius: 8px;
    animation: slideIn 0.3s ease;
  }
  @keyframes slideIn {
    from { transform: translateY(-10px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
  }
  body.dark .calendar-popup {
    background: #2c2c2c;
    border-color: #444;
  }
  
  /* Calendar Grid */
  .calendar-days,
  .calendar {
    display: grid;
    grid-template-columns: repeat(7, 35px);
    gap: 6px;
    text-align: center;
  }
  .calendar-days {
    font-weight: 500;
    color: #34495e;
    margin-bottom: 5px;
  }
  body.dark .calendar-days {
    color: #bdc3c7;
  }
  .calendar div {
    padding: 8px;
    cursor: pointer;
    border-radius: 4px;
    transition: background 0.2s ease, transform 0.2s ease;
  }
  .calendar div:hover {
    background: rgba(52, 152, 219, 0.1);
    transform: scale(1.05);
  }
  body.dark .calendar div:hover {
    background: rgba(255, 255, 255, 0.1);
  }
  .selected {
    background: var(--primary-color);
    color: white;
    box-shadow: 0 0 10px rgba(52, 152, 219, 0.5);
  }
  
  /* Buttons */
  .button-group {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    justify-content: center;
    margin-top: 20px;
  }
  .button-center {
    text-align: center;
    margin-top: 20px;
  }
  button {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    background: linear-gradient(135deg, #6a11cb, var(--primary-color));
    color: white;
    font-size: 1rem;
    font-weight: 600;
    transition: background 0.3s ease, transform 0.2s ease;
    box-shadow: var(--shadow-light);
  }
  button:hover {
    background: linear-gradient(135deg, #4e0ccf, #1a66d3);
    transform: scale(1.05);
  }
  button:focus {
    outline: none;
    box-shadow: 0 0 8px rgba(52, 152, 219, 0.5);
  }
  
  /* Sections */
  .section {
    margin-top: 30px;
    padding: 25px;
    border-radius: 12px;
    background: white;
    box-shadow: var(--shadow-light);
    transition: box-shadow 0.3s ease, transform 0.3s ease;
  }
  body.dark .section {
    background: #2c2c2c;
    box-shadow: var(--shadow-dark);
  }
  .section:hover {
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.2);
    transform: translateY(-2px);
  }
  
  /* Labels and Inputs */
  label {
    display: block;
    margin-bottom: 8px;
    color: #34495e;
    font-weight: 500;
  }
  body.dark label {
    color: #bdc3c7;
  }
  input[type="number"] {
    width: 100%;
    padding: 12px;
    margin-bottom: 15px;
    border: 1px solid #ddd;
    border-radius: 6px;
    font-size: 16px;
    box-sizing: border-box;
  }
  input[type="number"]:focus {
    border-color: var(--primary-color);
    outline: none;
    box-shadow: 0 0 8px rgba(52, 152, 219, 0.5);
  }
  body.dark input[type="number"] {
    background: #333;
    border-color: #444;
    color: #e0e0e0;
  }
  
  /* Selected Dates Text */
  .selected-dates {
    margin: 15px 0;
    font-size: 0.95em;
    color: #7f8c8d;
  }
  
  /* Nav & Calendar Header */
  .nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 10px;
  }
  .nav button {
    padding: 5px 10px;
    font-size: 0.9em;
  }
  
  /* Result Sections */
  #result, #reverseResult, #planner {
    margin-top: 15px;
    font-weight: 500;
    color: #27ae60;
  }
  
  /* Toggle Dark Button */
  .toggle-dark {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 8px 16px;
    background: linear-gradient(135deg, #34495e, #2c3e50);
    border-radius: 8px;
    box-shadow: var(--shadow-light);
  }
  .toggle-dark:hover {
    background: linear-gradient(135deg, #2c3e50, #1f2d3d);
    transform: scale(1.05);
  }
  
  /* Mode Switch */
  .mode-switch {
    margin: 20px 0;
    display: flex;
    gap: 20px;
  }
  .mode-switch label {
    display: flex;
    align-items: center;
    gap: 5px;
    color: #34495e;
  }
  body.dark .mode-switch label {
    color: #bdc3c7;
  }
  
  /* Footer */
  footer {
    text-align: center;
    margin-top: 40px;
    color: #7f8c8d;
    font-size: 0.9em;
    padding: 20px 0;
    background: linear-gradient(135deg, #f5f5f5, #e9d8d8);
    border-top: 1px solid #ddd;
    box-shadow: 0 -2px 10px rgba(0, 0, 0, 0.1);
  }
  footer:hover {
    box-shadow: 0 -4px 20px rgba(0, 0, 0, 0.2);
  }
  
  /* Utility */
  .hidden {
    display: none;
  }
  
  /* Responsive Design */
  @media (max-width: 600px) {
    .container {
      padding: 20px;
      max-width: 100%;
    }
    .section {
      padding: 15px;
    }
    h2 { font-size: 1.5em; }
    h3 { font-size: 1.2em; }
    button {
      width: 100%;
      margin: 5px 0;
    }
  }