/* ==========================================
   Variables CSS
   ========================================== */
   :root {
    --color-primary: #0077cc;
    --color-text: #111;
    --color-text-light: #555;
    --color-bg-card: #f5f5f5;
    --color-bg-sidebar: #f0f4f8;
    --color-bg-code: #eaeaea;
    --color-bg-example: #e0e5eb;
    --color-bg-pill: #d0e8ff;
    --color-code-inline: #d97706;
    --color-code-inline-bg: #fff4e6;
    --spacing-xs: 4px;
    --spacing-sm: 8px;
    --spacing-md: 12px;
    --spacing-lg: 16px;
    --spacing-xl: 20px;
    --spacing-2xl: 24px;
    --border-radius-sm: 6px;
    --border-radius-md: 8px;
    --border-radius-lg: 10px;
    --shadow-card: 0 6px 24px rgba(0, 0, 0, 0.1);
  }
  
  /* ==========================================
     Reset & Base Styles
     ========================================== */
  * {
    -webkit-tap-highlight-color: rgba(0, 119, 204, 0.1);
  }
  
  body {
    font-family: Inter, ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: white;
    color: var(--color-text);
    margin: 0;
    padding: var(--spacing-lg);
    font-size: 16px;
    line-height: 1.6;
  }
  
  @media (min-width: 768px) {
    body {
      padding: 32px;
    }
  }
  
  /* ==========================================
     Container
     ========================================== */
  .container {
    max-width: 100%;
    margin: 0 auto;
  }
  
  @media (min-width: 768px) {
    .container {
      max-width: 1100px;
    }
  }
  
  /* ==========================================
     Page Header
     ========================================== */
  .page-header {
    background: var(--color-bg-card);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-card);
    margin-bottom: var(--spacing-xl);
  }
  
  @media (min-width: 768px) {
    .page-header {
      padding: var(--spacing-2xl);
      margin-bottom: 28px;
    }
  }
  
  .page-header h1 {
    margin: 0 0 var(--spacing-sm);
    font-size: 1.5rem;
    color: var(--color-primary);
    line-height: 1.3;
  }
  
  @media (min-width: 768px) {
    .page-header h1 {
      font-size: 1.8rem;
    }
  }
  
  .subtitle {
    margin: 0;
    color: var(--color-text-light);
    font-size: 0.95rem;
  }
  
  /* ==========================================
     Navigation
     ========================================== */
  .exercises-nav {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
    position: sticky;
    top: 0;
    background: white;
    z-index: 10;
    padding: var(--spacing-md) 0;
    border-bottom: 1px solid var(--color-bg-example);
  }
  
  @media (min-width: 768px) {
    .exercises-nav {
      margin-bottom: 28px;
    }
  }
  
  .nav-link {
    display: inline-flex;
    align-items: center;
    min-height: 44px;
    padding: 10px 14px;
    text-decoration: none;
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.9rem;
    background: var(--color-bg-example);
    border-radius: var(--border-radius-sm);
    transition: all 0.2s ease;
  }
  
  @media (min-width: 768px) {
    .nav-link {
      font-size: 1rem;
      background: transparent;
    }
  }
  
  .nav-link:hover {
    text-decoration: underline;
    opacity: 0.8;
  }
  
  .nav-link:active {
    opacity: 0.7;
  }
  
  /* ==========================================
     Exercise Cards
     ========================================== */
  .exercise-card {
    background: var(--color-bg-card);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-card);
    margin-bottom: var(--spacing-xl);
  }
  
  @media (min-width: 768px) {
    .exercise-card {
      padding: var(--spacing-xl);
      margin-bottom: 22px;
    }
  }
  
  .exercise-header {
    margin-bottom: var(--spacing-lg);
  }
  
  .exercise-description {
    margin: var(--spacing-md) 0 0;
    padding: var(--spacing-md);
    background: rgba(0, 119, 204, 0.05);
    border-left: 3px solid var(--color-primary);
    border-radius: 4px;
    color: var(--color-text-light);
    font-size: 0.95rem;
    line-height: 1.7;
  }
  
  @media (min-width: 768px) {
    .exercise-description {
      font-size: 1rem;
    }
  }
  
  .exercise-badge {
    display: inline-block;
    padding: 6px 10px;
    border-radius: 999px;
    background: var(--color-bg-pill);
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.8rem;
    margin-bottom: var(--spacing-sm);
  }
  
  @media (min-width: 768px) {
    .exercise-badge {
      font-size: 0.875rem;
    }
  }
  
  h2 {
    margin: var(--spacing-sm) 0 var(--spacing-md);
    color: var(--color-text);
    font-size: 1.25rem;
    line-height: 1.4;
  }
  
  @media (min-width: 768px) {
    h2 {
      font-size: 1.5rem;
    }
  }
  
  h3 {
    margin: var(--spacing-lg) 0 var(--spacing-md);
    color: var(--color-text);
    font-size: 1.1rem;
  }
  
  @media (min-width: 768px) {
    h3 {
      font-size: 1.25rem;
    }
  }
  
  /* ==========================================
     Exercise Content Grid
     ========================================== */
  .exercise-content {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  @media (min-width: 900px) {
    .exercise-content {
      grid-template-columns: 1fr 340px;
      gap: 18px;
    }
  }
  
  /* En móviles, mostrar sidebar primero */
  @media (max-width: 899px) {
    .exercise-content {
      display: flex;
      flex-direction: column;
    }
    
    .exercise-sidebar {
      order: -1;
    }
  }
  
  .exercise-main {
    min-width: 0; /* Permite que el contenido se ajuste */
  }
  
  /* ==========================================
     Sidebar
     ========================================== */
  .exercise-sidebar {
    background: var(--color-bg-sidebar);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-md);
  }
  
  @media (min-width: 768px) {
    .exercise-sidebar {
      padding: 14px;
    }
  }
  
  .note-text {
    font-size: 0.95rem;
    color: var(--color-text-light);
    margin: 0 0 var(--spacing-md);
  }
  
  .tip-box {
    background: var(--color-bg-example);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-md);
    color: var(--color-text-light);
    font-size: 0.95rem;
    margin-top: var(--spacing-md);
  }
  
  /* ==========================================
     Lists
     ========================================== */
  ul {
    padding-left: 20px;
    margin: var(--spacing-md) 0;
  }
  
  @media (min-width: 768px) {
    ul {
      padding-left: 24px;
    }
  }
  
  li {
    margin-bottom: var(--spacing-sm);
    line-height: 1.6;
  }
  
  /* ==========================================
     Code Blocks
     ========================================== */
  code {
    background: var(--color-code-inline-bg);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.9em;
    font-family: Menlo, Monaco, 'Courier New', monospace;
    word-break: break-word;
    color: var(--color-code-inline);
    font-weight: 500;
  }
  
  pre {
    margin: var(--spacing-lg) 0;
  }
  
  .code-block {
    display: block;
    background: var(--color-bg-code);
    padding: var(--spacing-md);
    border-radius: var(--border-radius-md);
    overflow-x: auto;
    overflow-y: hidden;
    color: var(--color-text);
    font-family: Menlo, Monaco, 'Courier New', monospace;
    font-size: 0.85rem;
    line-height: 1.5;
    white-space: pre;
    word-wrap: normal;
    -webkit-overflow-scrolling: touch;
  }
  
  @media (min-width: 768px) {
    .code-block {
      font-size: 0.95rem;
      padding: 14px;
    }
  }
  
  /* ==========================================
     Footer
     ========================================== */
  .page-footer {
    background: var(--color-bg-card);
    padding: var(--spacing-lg);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-card);
    margin-top: var(--spacing-xl);
    text-align: center;
  }
  
  @media (min-width: 768px) {
    .page-footer {
      padding: var(--spacing-xl);
    }
  }
  
  .page-footer a {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
  }
  
  .page-footer a:hover {
    text-decoration: underline;
  }
  
  .page-footer a:active {
    opacity: 0.7;
  }
  
  /* ==========================================
     Responsive: Dispositivos muy pequeños
     ========================================== */
  @media (max-width: 380px) {
    body {
      padding: var(--spacing-md);
      font-size: 15px;
    }
    
    .page-header h1 {
      font-size: 1.3rem;
    }
    
    .exercise-badge {
      font-size: 0.75rem;
      padding: 4px 8px;
    }
    
    h2 {
      font-size: 1.1rem;
    }
    
    .code-block {
      font-size: 0.8rem;
    }
  }

  /* Estilos para compatibilidad con estructura existente */
  header {
    background: var(--color-bg-card);
    padding: var(--spacing-xl);
    border-radius: var(--border-radius-lg);
    box-shadow: var(--shadow-card);
    margin-bottom: var(--spacing-xl);
  }

  header h1 {
    margin: 0 0 var(--spacing-sm);
    font-size: 1.5rem;
    color: var(--color-primary);
    line-height: 1.3;
  }

  @media (min-width: 768px) {
    header h1 {
      font-size: 1.8rem;
    }
  }

  .nav-button {
    display: inline-flex;
    align-items: center;
    min-height: 44px;
    padding: 10px 14px;
    text-decoration: none;
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.9rem;
    background: var(--color-bg-example);
    border-radius: var(--border-radius-sm);
    transition: all 0.2s ease;
    margin-top: var(--spacing-sm);
  }

  @media (min-width: 768px) {
    .nav-button {
      font-size: 1rem;
    }
  }

  .nav-button:hover {
    text-decoration: underline;
    opacity: 0.8;
  }

  .problem-statement, .explanation, .solution-diagram, .source-code, .test-results {
    margin: var(--spacing-lg) 0;
  }

  .test-table {
    width: 100%;
    border-collapse: collapse;
    margin: 1rem 0;
    background: white;
    border-radius: var(--border-radius-md);
    overflow: hidden;
  }

  .test-table th, .test-table td {
    border: 1px solid var(--color-bg-example);
    padding: var(--spacing-md);
    text-align: left;
  }

  .test-table th {
    background: var(--color-bg-card);
    color: var(--color-text);
    font-weight: 600;
  }

  .test-table tr:nth-child(even) {
    background: #fafafa;
  }

  .test-table tr:hover {
    background: var(--color-bg-example);
  }

  img {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius-md);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
  }

  section {
    margin: var(--spacing-xl) 0;
  }

  p {
    line-height: 1.7;
    margin: var(--spacing-md) 0;
  }

  strong {
    color: var(--color-text);
    font-weight: 600;
  }

  .formula {
    background: var(--color-bg-example);
    padding: var(--spacing-md);
    border-left: 4px solid var(--color-primary);
    margin: var(--spacing-md) 0;
    font-family: Menlo, Monaco, 'Courier New', monospace;
    border-radius: var(--border-radius-sm);
  }

  ol {
    padding-left: 24px;
    margin: var(--spacing-md) 0;
  }

  ol li {
    margin-bottom: var(--spacing-sm);
    line-height: 1.6;
  }