:root {
      --light-bg: #f5f7fa;
      --light-text: #1a1a1a;
      --light-card: #ffffff;
      --light-accent: #1976d2;
      --light-hover: #1565c0;
      --dark-bg: #121212;
      --dark-text: #e0e0e0;
      --dark-card: #1f1f1f;
      --dark-accent: #90caf9;
      --dark-hover: #64b5f6;
      --danger: #e53935;
    }
    body {
      margin: 0;
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
      background-color: var(--light-bg);
      color: var(--light-text);
      transition: all 0.3s ease;
    }
    body.dark {
      background-color: var(--dark-bg);
      color: var(--dark-text);
    }
    header {
      background-color: var(--light-accent);
      color: white;
      padding: 1.2rem 2rem;
      font-size: 2rem;
      font-weight: 600;
      text-align: center;
      position: relative;
      transition: background-color 0.3s ease;
    }
    body.dark header {
      background-color: var(--dark-accent);
    }
    

    .theme-toggle {
      position: absolute;
      right: 1rem;
      top: 1rem;
      background: transparent;
      border: none;
      font-size: 1.7rem;
      cursor: pointer;
      color: white;
    }
    .auth-buttons {
      position: absolute;
      right: 4.5rem;
      top: 50%;
      transform: translateY(-50%);
      display: flex;
      gap: 1.2rem;
    }
    .auth-buttons a {
      background-color: white;
      color: var(--light-accent);
      padding: 0.3rem 0.8rem;
      border-radius: 6px;
      text-decoration: none;
      font-weight: 600;
      font-size: 0.9rem;
    }
    .container {
      max-width: 1000px;
      margin: 2rem auto;
      background: var(--light-card);
      padding: 2rem;
      border-radius: 12px;
      box-shadow: 0 4px 15px rgba(0,0,0,0.1);
      transition: background-color 0.3s ease;
    }
    body.dark .container {
      background: var(--dark-card);
    }
    .form-group {
      margin-bottom: 1.5rem;
    }
    label {
      display: block;
      margin-bottom: 0.5rem;
      font-weight: 600;
      font-size: 1rem;
    }
    select, input[type="date"], input[type="month"] {
      width: 100%;
      padding: 0.6rem;
      font-size: 1rem;
      border-radius: 6px;
      border: 1px solid #ccc;
    }
    table {
      width: 100%;
      border-collapse: collapse;
      margin-top: 2rem;
      border-radius: 8px;
      overflow: hidden;
    }
    th, td {
      border: 1px solid #ddd;
      padding: 0.75rem;
      text-align: center;
    }
    th {
      background-color: var(--light-accent);
      color: white;
      font-weight: 600;
    }
    body.dark th {
      background-color: var(--dark-accent);
    }
    .btn {
      background-color: var(--light-accent);
      color: white;
      border: none;
      padding: 0.6rem 1.2rem;
      border-radius: 6px;
      cursor: pointer;
      font-weight: 600;
      transition: background 0.3s ease;
    }
    .btn:hover {
      background-color: var(--light-hover);
    }
    body.dark .btn {
      background-color: var(--dark-accent);
    }
    body.dark .btn:hover {
      background-color: var(--dark-hover);
    }
    .danger {
      color: var(--danger);
      font-weight: bold;
    }
    .center-btn, .top-actions {
      display: flex;
      justify-content: center;
      flex-wrap: wrap;
      gap: 0.8rem;
      margin-top: 1rem;
    }
    .modal {
      position: fixed;
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      background: white;
      color: black;
      padding: 2rem;
      border-radius: 10px;
      box-shadow: 0 4px 10px rgba(0,0,0,0.2);
      z-index: 1000;
      display: none;
    }
    .modal.active {
      display: block;
    }
    .overlay {
      position: fixed;
      top: 0;
      left: 0;
      width: 100vw;
      height: 100vh;
      background: rgba(0, 0, 0, 0.5);
      z-index: 999;
      display: none;
    }
    .overlay.active {
      display: block;
    }