:root {
      --primary: #1a759f;
      --secondary: #6bd4c8;
      --accent-green: #2ecc71;
      --accent-orange: #f39c12;
      --light-bg: #f8fafc;
      --card-bg: #fff;
      --text-dark: #2d3748;
      --text-light: #718096;
      --shadow: 0 4px 12px rgba(0,0,0,0.08);
      --border: 1px solid #e2e8f0;
    }

    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
      font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    }

    body {
      background: var(--light-bg);
      min-height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      padding: 20px;
    }

    .auth-container {
      width: 100%;
      max-width: 420px;
      background: var(--card-bg);
      border-radius: 12px;
      box-shadow: var(--shadow);
      overflow: hidden;
      position: relative;
    }

    .auth-header {
      background: var(--primary);
      color: white;
      padding: 24px 32px;
      text-align: center;
      font-size: 24px;
      font-weight: 600;
      display: flex;
      align-items: center;
      gap: 12px;
    }

    .auth-form {
      padding: 32px;
    }

    .form-group {
      margin-bottom: 20px;
    }

    label {
      display: block;
      margin-bottom: 8px;
      color: var(--text-dark);
      font-weight: 500;
    }

    input {
      width: 100%;
      padding: 12px 16px;
      border: var(--border);
      border-radius: 8px;
      font-size: 16px;
      transition: border-color 0.2s;
      background: #fafafa;
    }

    input:focus {
      outline: none;
      border-color: var(--primary);
      box-shadow: 0 0 0 2px rgba(26, 117, 159, 0.1);
    }

    button {
      width: 100%;
      padding: 12px;
      background: var(--primary);
      color: white;
      border: none;
      border-radius: 8px;
      font-size: 16px;
      font-weight: 600;
      cursor: pointer;
      transition: background 0.2s;
      margin-top: 16px;
    }

    button:hover {
      background: #16658a;
    }

    .message {
      text-align: center;
      margin-top: 12px;
      min-height: 20px;
      font-size: 14px;
      font-weight: 500;
    }

    .auth-footer {
      text-align: center;
      padding: 24px;
      border-top: var(--border);
      color: var(--text-light);
      font-size: 14px;
    }

    .auth-footer a {
      color: var(--primary);
      text-decoration: none;
      font-weight: 600;
    }

    .toggle-section {
      display: flex;
      justify-content: center;
      gap: 16px;
      margin: 20px 0;
      padding: 16px 0;
      border-bottom: var(--border);
    }

    .toggle-btn {
      background: none;
      border: none;
      padding: 8px 16px;
      font-size: 14px;
      cursor: pointer;
      color: var(--text-light);
      transition: color 0.2s;
    }

    .toggle-btn.active {
      color: var(--primary);
      font-weight: 600;
      border-bottom: 2px solid var(--primary);
    }

    #registerForm, #loginForm {
      display: none;
    }

    #loginForm.active, #registerForm.active {
      display: block;
    }

    @media (max-width: 480px) {
      .auth-container { margin: 16px; }
      .auth-form { padding: 24px; }
    }

    /* Dark mode */
    [data-theme="dark"] {
      --light-bg: #1a202c;
      --card-bg: #2d3748;
      --text-dark: #f7fafc;
      --text-light: #a0aec0;
      --border: 1px solid #4a5568;
      --shadow: 0 4px 12px rgba(0,0,0,0.3);
    }

    [data-theme="dark"] .auth-form input {
      background: #4a5568;
      color: white;
    }

    [data-theme="dark"] .auth-form input:focus {
      box-shadow: 0 0 0 2px rgba(26, 117, 159, 0.2);
    }