/* --- 1. Design System & Variables --- */
:root {
    /* Color Palette */
    --color-background: #f0f2f5;
    --color-surface: #ffffff;
    --color-primary: #0052cc;
    --color-primary-hover: #0065ff;
    --color-text-main: #172b4d;
    --color-text-secondary: #5e6c84;
    --color-border: #dfe1e6;
    --color-accent-red: #de350b;
  
    /* Typography */
    --font-family-main: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
      Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-size-base: 16px;
    --line-height-base: 1.6;
  
    /* Spacing & Sizing */
    --spacing-unit: 8px;
    --border-radius: 6px;
    --max-width: 960px;
  
    /* Shadows & Effects */
    --shadow-sm: 0 1px 2px rgba(23, 43, 77, 0.1);
    --shadow-md: 0 4px 8px -2px rgba(23, 43, 77, 0.12),
      0 0 1px rgba(23, 43, 77, 0.12);
    --shadow-lg: 0 10px 20px -5px rgba(23, 43, 77, 0.15),
      0 0 1px rgba(23, 43, 77, 0.15);
    --transition-speed: 0.2s ease-in-out;
  }
  
  /* --- 2. Global Resets & Base Styles --- */
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  body {
    font-family: var(--font-family-main);
    font-size: var(--font-size-base);
    line-height: var(--line-height-base);
    color: var(--color-text-main);
    background-color: var(--color-background);
    /* Subtle noise texture for a premium feel */
    background-image: url("data:image/svg+xml,%3Csvg width='6' height='6' viewBox='0 0 6 6' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='%239C92AC' fill-opacity='0.07' fill-rule='evenodd'%3E%3Cpath d='M5 0h1L0 6V5zM6 5v1H5z'/%3E%3C/g%3E%3C/svg%3E");
  }
  
  a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-speed);
  }
  
  a:hover {
    color: var(--color-primary-hover);
    text-decoration: underline;
  }
  
  h1,
  h2,
  h3,
  h4,
  h5,
  h6 {
    font-weight: 700;
    line-height: 1.2;
  }
  
  /* --- 3. Layout & Header/Footer --- */
  header,
  main,
  footer {
    width: 100%;
    max-width: var(--max-width);
    margin: 0 auto;
    padding: calc(var(--spacing-unit) * 3) calc(var(--spacing-unit) * 2);
  }
  
  /* Utility class for full-width containers, with appropriate padding */
  main.container-fluid {
    max-width: none;
    padding-left: 0;
    padding-right: 0;
  }
  
  header {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--color-border);
    padding-top: calc(var(--spacing-unit) * 4);
    padding-bottom: calc(var(--spacing-unit) * 4);
    gap: calc(var(--spacing-unit) * 2);
  }
  
  header h1 {
    font-size: 2.5rem;
    color: var(--color-text-main);
  }
  
  .version-info {
    font-size: 1rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    vertical-align: middle;
    margin-left: var(--spacing-unit);
  }
  
  header h2 {
    font-size: 1rem;
    font-weight: 400;
    color: var(--color-text-secondary);
    flex-basis: 100%;
    margin-top: calc(var(--spacing-unit) * -2);
  }
  
  header nav {
    display: flex;
    gap: calc(var(--spacing-unit) * 3);
  }
  
  header nav a {
    font-weight: 500;
    font-size: 1.1rem;
  }
  
  header nav a.active {
    color: var(--color-text-main);
    font-weight: 700;
    text-decoration: none;
    cursor: default;
  }

  .search-container {
    flex-grow: 1;
    display: flex;
    justify-content: center;
    margin: 0 calc(var(--spacing-unit) * 4);
  }
  
  #search-form {
    display: flex;
    width: 100%;
    max-width: 450px;
  }
  
  #search-input {
    width: 100%;
    padding: var(--spacing-unit) calc(var(--spacing-unit) * 2);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius) 0 0 var(--border-radius);
    font-size: 1rem;
    transition: all var(--transition-speed);
  }
  
  #search-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 101, 255, 0.2);
    position: relative; /* Ensures shadow is not clipped by the button */
  }
  
  #search-form button {
    padding: 0 calc(var(--spacing-unit) * 2);
    border: 1px solid var(--color-border);
    border-left: none;
    background-color: var(--color-surface);
    cursor: pointer;
    border-radius: 0 var(--border-radius) var(--border-radius) 0;
    transition: background-color var(--transition-speed);
    color: var(--color-text-secondary); /* For SVG color */
  }
  
  #search-form button:hover {
    background-color: var(--color-primary);
    border-color: var(--color-primary);
    color: var(--color-surface); /* For SVG color on hover */
  }
  
  #auth-container {
    display: flex;
    align-items: center;
    gap: var(--spacing-unit);
  }
  
  #auth-container .login-link,
  #logout-button {
    background-color: var(--color-primary);
    color: var(--color-surface);
    padding: var(--spacing-unit) calc(var(--spacing-unit) * 2);
    border-radius: var(--border-radius);
    text-decoration: none;
    border: none;
    cursor: pointer;
    font-family: var(--font-family-main);
    font-size: 0.9rem;
    font-weight: 500;
    transition: background-color var(--transition-speed);
  }
  
  #auth-container .login-link:hover,
  #logout-button:hover {
    background-color: var(--color-primary-hover);
    text-decoration: none;
  }
  
  footer {
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 0.9rem;
    padding-top: calc(var(--spacing-unit) * 4);
    padding-bottom: calc(var(--spacing-unit) * 4);
  }
  
  /* --- 4. Main Content & Post Styling --- */
  main {
    display: grid;
    gap: calc(var(--spacing-unit) * 4);
  }
  
  main > p {
    /* For Loading/Error messages */
    text-align: center;
    color: var(--color-text-secondary);
    font-size: 1.2rem;
    padding: calc(var(--spacing-unit) * 5) 0;
  }
  
  article {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    padding: calc(var(--spacing-unit) * 4);
    box-shadow: var(--shadow-md);
    transition: transform var(--transition-speed),
      box-shadow var(--transition-speed);
  }
  
  article:not(#single-post-article):hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
  }
  
  .post-header {
    margin-bottom: calc(var(--spacing-unit) * 3);
  }
  
  .post-header h2 {
    font-size: 1.8rem;
    margin-bottom: var(--spacing-unit);
  }
  
  .post-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: var(--spacing-unit);
    color: var(--color-text-secondary);
    font-size: 0.9rem;
  }
  
  .post-actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-unit);
    font-size: 0.9rem;
  }
  
  .post-content {
    margin-top: calc(var(--spacing-unit) * 2);
  }
  
  .post-content p {
    margin-bottom: var(--spacing-unit);
  }
  
  .post-content h3,
  .post-content h4 {
    margin-top: calc(var(--spacing-unit) * 3);
    margin-bottom: var(--spacing-unit);
  }
  
  .post-content ul,
  .post-content ol {
    margin-left: calc(var(--spacing-unit) * 3);
    margin-bottom: var(--spacing-unit);
  }
  
  .post-content blockquote {
    border-left: 4px solid var(--color-border);
    padding-left: calc(var(--spacing-unit) * 2);
    margin: calc(var(--spacing-unit) * 2) 0;
    color: var(--color-text-secondary);
  }
  
  .post-content code {
    background-color: var(--color-background);
    padding: 2px 6px;
    border-radius: 4px;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  }
  
  /* --- 5. Form & Auth Page Styling --- */
  .auth-page,
  .create-post-page {
    padding-top: calc(var(--spacing-unit) * 5);
    padding-bottom: calc(var(--spacing-unit) * 5);
  }
  
  .auth-wrapper {
    max-width: 450px;
    margin: 0 auto;
    background-color: var(--color-surface);
    padding: calc(var(--spacing-unit) * 4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
  }
  
  .form-wrapper {
    margin: 0 auto;
    background-color: var(--color-surface);
    padding: calc(var(--spacing-unit) * 4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
  }
  
  /* This rule is specific enough to override the default 450px form width and allows the form to be fully fluid. */
  main.create-post-page .form-wrapper {
    max-width: 1400px; /* Wider form for better writing experience */
    margin: 2rem auto;
    background: var(--color-surface);
    padding: 3rem;
    border-radius: 12px;
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.08);
  }
  
  .form-wrapper h1 {
    font-size: 1.8rem;
    text-align: center;
    margin-bottom: calc(var(--spacing-unit) * 3);
  }
  
  .auth-tabs {
    display: flex;
    margin-bottom: calc(var(--spacing-unit) * 3);
    border-bottom: 1px solid var(--color-border);
  }
  
  .auth-tabs button {
    flex: 1;
    padding: calc(var(--spacing-unit) * 2);
    border: none;
    background-color: transparent;
    font-size: 1rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition-speed);
    border-bottom: 3px solid transparent;
  }
  
  .auth-tabs button.active {
    color: var(--color-primary);
    border-bottom-color: var(--color-primary);
  }
  
  #auth-form,
  #new-post-form,
  #edit-post-form {
    display: flex;
    flex-direction: column;
    gap: calc(var(--spacing-unit) * 2.5);
  }
  
  .form-group {
    display: flex;
    flex-direction: column;
  }
  
  .form-group label {
    font-weight: 500;
    margin-bottom: var(--spacing-unit);
  }
  
  input[type="email"],
  input[type="password"],
  input[type="text"],
  textarea {
    width: 100%;
    padding: calc(var(--spacing-unit) * 1.5);
    border: 1px solid var(--color-border);
    border-radius: var(--border-radius);
    font-family: var(--font-family-main);
    font-size: 1rem;
    transition: border-color var(--transition-speed),
      box-shadow var(--transition-speed);
  }
  
  input[type="email"]:focus,
  input[type="password"]:focus,
  input[type="text"]:focus,
  textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 101, 255, 0.2);
  }
  
  textarea {
    resize: vertical;
    min-height: 400px; /* Taller content box */
  }
  
  #auth-submit-button,
  #new-post-form button,
  #edit-post-form button {
    background-color: var(--color-primary);
    color: var(--color-surface);
    padding: calc(var(--spacing-unit) * 1.5);
    border-radius: var(--border-radius);
    border: none;
    cursor: pointer;
    font-family: var(--font-family-main);
    font-size: 1rem;
    font-weight: 500;
    transition: background-color var(--transition-speed);
    margin-top: var(--spacing-unit);
  }
  
  #auth-submit-button:hover,
  #new-post-form button:hover,
  #edit-post-form button:hover {
    background-color: var(--color-primary-hover);
  }
  
  .error-message {
    color: var(--color-accent-red);
    background-color: rgba(222, 53, 11, 0.1);
    padding: var(--spacing-unit);
    border-radius: var(--border-radius);
    text-align: center;
    font-size: 0.9rem;
  }
  
  /* --- 6. Older Posts List Styling --- */
  .older-posts {
    background-color: var(--color-surface);
    border-radius: var(--border-radius);
    padding: calc(var(--spacing-unit) * 3) calc(var(--spacing-unit) * 4);
    box-shadow: var(--shadow-sm);
    margin-top: calc(var(--spacing-unit) * 2);
  }
  
  .older-posts h3 {
    font-size: 1.5rem;
    color: var(--color-text-main);
    margin-bottom: calc(var(--spacing-unit) * 2);
    padding-bottom: var(--spacing-unit);
    border-bottom: 1px solid var(--color-border);
  }
  
  .older-posts-list {
    list-style: none;
    padding: 0;
  }
  
  .older-posts-list li {
    padding: calc(var(--spacing-unit) * 1.5) 0;
    border-bottom: 1px solid var(--color-border);
    transition: background-color var(--transition-speed);
  }
  
  .older-posts-list li:last-child {
    border-bottom: none;
  }
  
  .older-posts-list li a {
    display: block;
    text-decoration: none;
  }
  
  /* --- 7. Single Post & Share Button Styling --- */
  .single-post-nav {
    margin-bottom: var(--spacing-unit);
  }
  
  .single-post-nav a {
    font-weight: 500;
    color: var(--color-text-secondary);
  }
  
  .action-button,
  .share-button { /* Keep .share-button for backward compatibility if needed */
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-unit);
    background-color: var(--color-background);
    border: 1px solid var(--color-border);
    color: var(--color-text-secondary);
    padding: calc(var(--spacing-unit) * 0.75) calc(var(--spacing-unit) * 1.5);
    border-radius: var(--border-radius);
    font-family: var(--font-family-main);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed);
  }
  
  .action-button:hover,
  .share-button:hover {
    background-color: var(--color-primary);
    color: var(--color-surface);
    border-color: var(--color-primary);
  }
  
  .action-button svg,
  .share-button svg {
    transition: transform var(--transition-speed);
  }
  .action-button:hover svg,
  .share-button:hover svg {
    transform: translateY(-2px);
  }

  .print-button:hover {
    background-color: var(--color-text-secondary);
    border-color: var(--color-text-secondary);
  }
  
  .edit-post-link {
    display: inline-flex;
    align-items: center;
    background-color: var(--color-background);
    color: var(--color-text-secondary);
    padding: calc(var(--spacing-unit) * 0.75) calc(var(--spacing-unit) * 1.5);
    border-radius: var(--border-radius);
    text-decoration: none;
    border: 1px solid var(--color-border);
    font-size: 0.9rem;
    font-weight: 500;
    transition: all var(--transition-speed);
  }
  
  .edit-post-link:hover {
    background-color: var(--color-text-secondary);
    color: var(--color-surface);
    border-color: var(--color-text-secondary);
    text-decoration: none;
  }
  
  .delete-post-btn {
    display: inline-flex;
    align-items: center;
    background-color: var(--color-background);
    color: var(--color-text-secondary);
    padding: calc(var(--spacing-unit) * 0.75) calc(var(--spacing-unit) * 1.5);
    border-radius: var(--border-radius);
    border: 1px solid var(--color-border);
    font-family: var(--font-family-main);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed);
  }
  
  .delete-post-btn:hover {
    background-color: var(--color-accent-red);
    color: var(--color-surface);
    border-color: var(--color-accent-red);
  }

  /* --- MODAL STYLES --- */
  .modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(23, 43, 77, 0.6);
    z-index: 1000;
    animation: fadeIn 0.3s forwards;
  }

  .modal-container {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0.95);
    background-color: var(--color-surface);
    padding: calc(var(--spacing-unit) * 4);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-lg);
    z-index: 1001;
    width: 90%;
    max-width: 500px;
    opacity: 0;
    animation: fadeInScaleUp 0.3s 0.1s forwards;
  }

  .modal-header h3 {
    font-size: 1.5rem;
    margin: 0;
  }

  .modal-body {
    margin: calc(var(--spacing-unit) * 3) 0;
    color: var(--color-text-secondary);
  }

  .modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: var(--spacing-unit);
  }

  .modal-btn {
    padding: var(--spacing-unit) calc(var(--spacing-unit) * 2);
    border: none;
    border-radius: var(--border-radius);
    font-family: var(--font-family-main);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed);
  }

  .modal-btn-secondary {
    background-color: var(--color-background);
    border: 1px solid var(--color-border);
    color: var(--color-text-secondary);
  }
  .modal-btn-secondary:hover {
    background-color: var(--color-border);
  }

  .modal-btn-danger {
    background-color: var(--color-accent-red);
    color: var(--color-surface);
  }

  /* --- 8. Post Navigation --- */
  .post-navigation {
    display: flex;
    justify-content: space-between;
    margin-top: calc(var(--spacing-unit) * 5);
    padding-top: calc(var(--spacing-unit) * 3);
    border-top: 1px solid var(--color-border);
  }
  
  .post-navigation a {
    font-weight: 500;
    color: var(--color-text-main);
    padding: var(--spacing-unit) calc(var(--spacing-unit) * 2);
    border-radius: var(--border-radius);
    transition: background-color var(--transition-speed);
  }
  
  .post-navigation a:hover {
    background-color: var(--color-background);
    text-decoration: none;
  }
  
  /* --- 9. Search Results Styling --- */
  .search-results-header {
    background-color: var(--color-surface);
    padding: calc(var(--spacing-unit) * 3);
    border-radius: var(--border-radius);
    margin-bottom: calc(var(--spacing-unit) * 4);
    box-shadow: var(--shadow-sm);
  }
  
  .search-results-header h2 {
    margin-bottom: var(--spacing-unit);
  }
  
  .search-results-header p {
    color: var(--color-text-secondary);
    margin-bottom: calc(var(--spacing-unit) * 2);
  }
  
  .clear-search-link {
    font-weight: 500;
  }
  
  main > article h3 {
    margin-bottom: var(--spacing-unit);
  }
  
  /* --- 10. About Page Styling --- */
  article .about-contact {
    margin-top: calc(var(--spacing-unit) * 4);
    padding: calc(var(--spacing-unit) * 4);
    background-color: var(--color-primary);
    border-radius: var(--border-radius);
    text-align: center;
    color: var(--color-surface);
    box-shadow: var(--shadow-lg);
    transition: transform var(--transition-speed);
  }
  
  article .about-contact p {
    margin-bottom: var(--spacing-unit);
    color: rgba(255, 255, 255, 0.85);
  }
  
  article .about-contact a {
    font-weight: 700;
    font-size: 1.1rem;
    word-break: break-all;
    color: var(--color-surface);
    text-decoration: underline;
  }

  /* --- 11. Animations --- */
  @keyframes fadeIn {
    to {
      opacity: 1;
    }
  }

  @keyframes fadeInScaleUp {
    to {
      opacity: 1;
      transform: translate(-50%, -50%) scale(1);
    }
  }