/**
 * Peptide News Feed — Public Styles (Redesigned)
 *
 * Premium, Apple-inspired news feed with refined typography,
 * generous spacing, and smooth micro-interactions.
 *
 * Design by: Senior Design Director
 * Redesign Date: 2026-04-07
 * @since 2.2.0
 */

/* Import Inter font from Google Fonts */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

/* ══════════════════════════════════════════════════════════════════
   CSS CUSTOM PROPERTIES (Variables)
   ══════════════════════════════════════════════════════════════════ */

:root {
  /* Neutral Scale — Light Mode */
  --pn-bg-primary: #ffffff;
  --pn-bg-secondary: #f9fafb;
  --pn-border-light: #e5e7eb;
  --pn-border-subtle: #d1d5db;

  /* Text Colors */
  --pn-text-primary: #111827;
  --pn-text-secondary: #4b5563;
  --pn-text-tertiary: #9ca3af;
  --pn-text-muted: #d1d5db;

  /* Accent Colors */
  --pn-accent-primary: #2563eb;
  --pn-accent-hover: #1d4ed8;
  --pn-source-color: #1f2937;
  --pn-source-bg: #f3f4f6;

  /* Focus & System */
  --pn-focus-ring: #2563eb;
  --pn-error: #dc2626;
  --pn-error-bg: #fee2e2;
  --pn-success: #16a34a;
  --pn-loading: #6b7280;
}

/* ────────────────────────────────────────────────────────────────
   DARK MODE OVERRIDE
   ────────────────────────────────────────────────────────────── */

@media (prefers-color-scheme: dark) {
  :root {
    /* Neutral Scale — Dark Mode */
    --pn-bg-primary: #0f172a;
    --pn-bg-secondary: #1e293b;
    --pn-border-light: #334155;
    --pn-border-subtle: #475569;

    /* Text Colors */
    --pn-text-primary: #f1f5f9;
    --pn-text-secondary: #cbd5e1;
    --pn-text-tertiary: #94a3b8;
    --pn-text-muted: #64748b;

    /* Accent Colors */
    --pn-accent-primary: #60a5fa;
    --pn-accent-hover: #93c5fd;
    --pn-source-color: #e2e8f0;
    --pn-source-bg: #1e293b;

    /* Focus & System */
    --pn-focus-ring: #60a5fa;
    --pn-error: #f87171;
    --pn-error-bg: #7f1d1d;
    --pn-success: #86efac;
    --pn-loading: #64748b;
  }
}

/* ══════════════════════════════════════════════════════════════════
   BASE TYPOGRAPHY & LAYOUT
   ══════════════════════════════════════════════════════════════════ */

.pn-news-feed {
  max-width: 900px;
  margin: 0 auto;
  padding: 40px 20px;
  font-family: Inter, -apple-system, BlinkMacSystemFont, 'Segoe UI',
    Roboto, 'Helvetica Neue', sans-serif;
  font-size: 16px;
  color: var(--pn-text-primary);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* ══════════════════════════════════════════════════════════════════
   ARTICLES LIST & CARD CONTAINER
   ══════════════════════════════════════════════════════════════════ */

.pn-articles-list {
  display: flex;
  flex-direction: column;
  gap: 0;
  list-style: none;
  padding: 0;
  margin: 0;
}

/* ────────────────────────────────────────────────────────────────
   ARTICLE CARD STRUCTURE
   ────────────────────────────────────────────────────────────── */

.pn-article {
  display: flex;
  flex-direction: column;
  padding: 24px;
  margin-bottom: 24px;
  gap: 12px;
  background: var(--pn-bg-primary);
  border: 1px solid var(--pn-border-light);
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
}

.pn-article:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 32px rgba(0, 0, 0, 0.12);
  border-color: var(--pn-border-subtle);
}

.pn-article:last-child {
  margin-bottom: 0;
}

/* ────────────────────────────────────────────────────────────────
   METADATA LINE (Source · Date)
   ────────────────────────────────────────────────────────────── */

.pn-article-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 6px;
  margin-bottom: 12px;
  font-size: 13px;
  font-weight: 500;
  color: var(--pn-text-tertiary);
  line-height: 1.3;
  letter-spacing: 0.2px;
}

.pn-source {
  display: inline-block;
  padding: 4px 8px;
  background: var(--pn-source-bg);
  color: var(--pn-source-color);
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  border-radius: 4px;
  transition: all 0.15s ease;
}

.pn-source:hover {
  background: color-mix(in srgb, var(--pn-source-bg) 80%, var(--pn-source-color) 20%);
  cursor: pointer;
}

.pn-separator {
  display: inline-block;
  font-size: 11px;
  color: var(--pn-border-light);
  margin: 0 2px;
}

.pn-date {
  font-size: 13px;
  color: var(--pn-text-tertiary);
}

/* ────────────────────────────────────────────────────────────────
   ARTICLE TITLE
   ────────────────────────────────────────────────────────────── */

.pn-article-title {
  margin: 0 0 14px 0;
  font-size: 22px;
  font-weight: 700;
  line-height: 1.4;
  letter-spacing: -0.3px;
  color: var(--pn-text-primary);
}

.pn-article-title a {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease, text-decoration 0.2s ease;
}

.pn-article-title a:hover {
  color: var(--pn-accent-primary);
  text-decoration: underline;
  text-decoration-thickness: 2px;
  text-underline-offset: 4px;
}

.pn-article-title a:focus-visible {
  outline: 2px solid var(--pn-focus-ring);
  outline-offset: 2px;
}

@media (prefers-color-scheme: dark) {
  .pn-article-title a:hover {
    color: var(--pn-accent-hover);
  }
}

/* ────────────────────────────────────────────────────────────────
   EXCERPT / SUMMARY
   ────────────────────────────────────────────────────────────── */

.pn-article-excerpt {
  margin: 0 0 14px 0;
  font-size: 15px;
  font-weight: 400;
  line-height: 1.7;
  color: var(--pn-text-secondary);
  display: -webkit-box;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 4;
  overflow: hidden;
  flex: 1;
}

/* ────────────────────────────────────────────────────────────────
   AUTHOR
   ────────────────────────────────────────────────────────────── */

.pn-author {
  margin: 0 0 10px 0;
  font-size: 13px;
  font-weight: 400;
  color: var(--pn-text-tertiary);
  line-height: 1.4;
}

.pn-author::before {
  content: '';
}

/* ══════════════════════════════════════════════════════════════════
   LOADING STATES & SKELETON
   ══════════════════════════════════════════════════════════════════ */

.pn-loading {
  display: flex;
  flex-direction: column;
  gap: 0;
  list-style: none;
  padding: 0;
  margin: 0;
}

.pn-skeleton-card {
  padding: 24px;
  margin-bottom: 24px;
  background: var(--pn-bg-primary);
  border: 1px solid var(--pn-border-light);
  border-radius: 8px;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.04);
}

.pn-skeleton-card:last-child {
  margin-bottom: 0;
}

.pn-skeleton-line {
  height: 12px;
  background: linear-gradient(
    90deg,
    var(--pn-loading) 0%,
    color-mix(in srgb, var(--pn-loading) 50%, transparent) 50%,
    var(--pn-loading) 100%
  );
  background-size: 200% 100%;
  border-radius: 4px;
  margin-bottom: 12px;
  animation: pn-shimmer 2s infinite;
}

/* Staggered animation delays for skeleton lines */
.pn-skeleton-meta {
  width: 40%;
  height: 10px;
  animation: pn-shimmer 2s infinite 0s;
}

.pn-skeleton-title {
  width: 85%;
  height: 18px;
  margin-bottom: 14px;
  animation: pn-shimmer 2s infinite 0.1s;
}

.pn-skeleton-excerpt {
  width: 100%;
  height: 14px;
  animation: pn-shimmer 2s infinite 0.2s;
}

.pn-skeleton-excerpt-short {
  width: 70%;
  height: 14px;
  animation: pn-shimmer 2s infinite 0.3s;
}

.pn-skeleton-author {
  width: 30%;
  height: 10px;
  margin-top: 12px;
  animation: pn-shimmer 2s infinite 0.4s;
}

@keyframes pn-shimmer {
  0% { background-position: 200% 0; }
  100% { background-position: -200% 0; }
}

/* ══════════════════════════════════════════════════════════════════
   ERROR STATE
   ══════════════════════════════════════════════════════════════════ */

.pn-error {
  display: block;
  padding: 20px;
  text-align: center;
  background: color-mix(in srgb, var(--pn-error-bg) 50%, transparent);
  border: 1px solid var(--pn-border-light);
  border-radius: 8px;
  color: var(--pn-error);
  font-size: 15px;
  line-height: 1.6;
}

.pn-error p {
  margin: 0 0 16px 0;
  font-size: 15px;
  font-weight: 400;
}

.pn-error p:last-child {
  margin-bottom: 0;
}

.pn-retry-btn {
  display: inline-block;
  padding: 10px 20px;
  margin-top: 16px;
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  color: #ffffff;
  background: var(--pn-error);
  border: none;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s ease;
}

.pn-retry-btn:hover {
  opacity: 0.9;
  transform: scale(1.01);
}

.pn-retry-btn:active {
  transform: scale(0.99);
}

.pn-retry-btn:focus-visible {
  outline: 2px solid var(--pn-focus-ring);
  outline-offset: 2px;
}

/* ══════════════════════════════════════════════════════════════════
   EMPTY STATE
   ══════════════════════════════════════════════════════════════════ */

.pn-empty {
  display: block;
  padding: 60px 20px;
  text-align: center;
  color: var(--pn-text-tertiary);
  font-size: 16px;
  font-weight: 400;
  line-height: 1.6;
}

.pn-empty p {
  margin: 0;
}

/* ══════════════════════════════════════════════════════════════════
   PAGINATION
   ══════════════════════════════════════════════════════════════════ */

.pn-pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  margin-top: 40px;
  padding-top: 24px;
  border-top: 1px solid var(--pn-border-light);
}

.pn-page-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 10px 16px;
  font-size: 14px;
  font-weight: 600;
  line-height: 1.4;
  color: var(--pn-text-primary);
  background: var(--pn-bg-primary);
  border: 1px solid var(--pn-border-light);
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.pn-page-btn:hover:enabled {
  border-color: var(--pn-accent-primary);
  color: var(--pn-accent-primary);
  background: var(--pn-bg-secondary);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.15);
}

.pn-page-btn:active:enabled {
  transform: translateY(0);
  box-shadow: 0 2px 4px rgba(37, 99, 235, 0.1);
  background: var(--pn-bg-secondary);
}

.pn-page-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.pn-page-btn:focus-visible {
  outline: 2px solid var(--pn-focus-ring);
  outline-offset: 2px;
}

.pn-page-info {
  font-size: 14px;
  font-weight: 500;
  line-height: 1.4;
  color: var(--pn-text-secondary);
  white-space: nowrap;
}

/* ══════════════════════════════════════════════════════════════════
   RESPONSIVE DESIGN — TABLET (768px - 1024px)
   ══════════════════════════════════════════════════════════════════ */

@media (min-width: 768px) and (max-width: 1023px) {
  .pn-news-feed {
    max-width: 100%;
    padding: 30px;
  }

  .pn-article {
    padding: 20px;
    gap: 12px;
    margin-bottom: 20px;
  }

  .pn-article-title {
    font-size: 20px;
    margin-bottom: 12px;
  }

  .pn-article-excerpt {
    margin-bottom: 12px;
  }

  .pn-skeleton-card {
    padding: 20px;
    margin-bottom: 20px;
  }
}

/* ══════════════════════════════════════════════════════════════════
   RESPONSIVE DESIGN — MOBILE (< 768px)
   ══════════════════════════════════════════════════════════════════ */

@media (max-width: 767px) {
  .pn-news-feed {
    max-width: 100%;
    padding: 20px 16px;
  }

  .pn-article {
    padding: 16px;
    gap: 10px;
    margin-bottom: 16px;
  }

  .pn-article-title {
    font-size: 18px;
    margin-bottom: 12px;
    line-height: 1.3;
    letter-spacing: -0.2px;
  }

  .pn-article-excerpt {
    font-size: 14px;
    line-height: 1.6;
    margin-bottom: 12px;
    -webkit-line-clamp: 3;
  }

  .pn-article-meta {
    gap: 6px;
    margin-bottom: 10px;
    font-size: 12px;
  }

  .pn-source {
    padding: 3px 6px;
    font-size: 12px;
  }

  .pn-author {
    margin-bottom: 8px;
    font-size: 12px;
  }

  .pn-skeleton-card {
    padding: 16px;
    margin-bottom: 16px;
  }

  .pn-pagination {
    flex-direction: column;
    gap: 12px;
  }

  .pn-page-btn {
    width: 100%;
    padding: 12px 16px;
  }

  .pn-page-info {
    width: 100%;
  }
}

/* ══════════════════════════════════════════════════════════════════
   SMALL MOBILE (< 480px)
   ══════════════════════════════════════════════════════════════════ */

@media (max-width: 479px) {
  .pn-news-feed {
    padding: 16px 12px;
  }

  .pn-article {
    padding: 12px;
    gap: 8px;
    margin-bottom: 12px;
  }

  .pn-article-title {
    font-size: 18px;
    margin-bottom: 10px;
  }

  .pn-article-excerpt {
    font-size: 14px;
    -webkit-line-clamp: 3;
  }

  .pn-article-meta {
    font-size: 12px;
    gap: 4px;
    margin-bottom: 8px;
  }

  .pn-skeleton-card {
    padding: 12px;
    margin-bottom: 12px;
  }
}

/* ══════════════════════════════════════════════════════════════════
   DARK MODE DARK MODE ENHANCEMENTS
   ══════════════════════════════════════════════════════════════════ */

@media (prefers-color-scheme: dark) {
  .pn-article {
    background: var(--pn-bg-primary);
    border-color: var(--pn-border-light);
  }

  .pn-article-title {
    color: var(--pn-text-primary);
  }

  .pn-article-excerpt {
    color: var(--pn-text-secondary);
  }

  .pn-article-meta {
    color: var(--pn-text-tertiary);
  }

  .pn-source {
    background: var(--pn-source-bg);
    color: var(--pn-source-color);
  }

  .pn-date {
    color: var(--pn-text-tertiary);
  }

  .pn-author {
    color: var(--pn-text-tertiary);
  }

  .pn-page-btn {
    background: transparent;
    border-color: var(--pn-border-light);
    color: var(--pn-text-primary);
  }

  .pn-page-btn:hover:enabled {
    border-color: var(--pn-accent-primary);
    color: var(--pn-accent-primary);
    background: transparent;
  }

  .pn-page-btn:disabled {
    color: var(--pn-text-muted);
    border-color: var(--pn-border-subtle);
  }

  .pn-page-info {
    color: var(--pn-text-secondary);
  }

  .pn-pagination {
    border-top-color: var(--pn-border-light);
  }

  .pn-error {
    background: color-mix(in srgb, var(--pn-error-bg) 40%, transparent);
    border-color: var(--pn-border-light);
    color: var(--pn-error);
  }

  .pn-retry-btn {
    background: var(--pn-error);
    color: #ffffff;
  }

  .pn-retry-btn:hover {
    opacity: 0.8;
  }

  .pn-empty {
    color: var(--pn-text-tertiary);
  }

  .pn-skeleton-line {
    background: linear-gradient(
      90deg,
      var(--pn-loading) 0%,
      color-mix(in srgb, var(--pn-loading) 50%, transparent) 50%,
      var(--pn-loading) 100%
    );
    background-size: 200% 100%;
  }

  .pn-skeleton-card {
    background: var(--pn-bg-primary);
    border-color: var(--pn-border-light);
  }
}

/* ══════════════════════════════════════════════════════════════════
   ACCESSIBILITY
   ══════════════════════════════════════════════════════════════════ */

/* High contrast mode support */
@media (prefers-contrast: more) {
  .pn-article {
    border-width: 2px;
  }

  .pn-page-btn {
    border-width: 2px;
  }

  .pn-article-title a:focus-visible,
  .pn-page-btn:focus-visible,
  .pn-retry-btn:focus-visible {
    outline-width: 3px;
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  .pn-article,
  .pn-article-title a,
  .pn-page-btn,
  .pn-retry-btn,
  .pn-skeleton-line {
    animation: none !important;
    transition: none !important;
  }
}