/* ===========================
   TABLET — 900px
   =========================== */
@media (max-width: 900px) {
  /* Landing page grids */
  .tech-cards,
  .news-grid,
  .team-grid { grid-template-columns: 1fr 1fr; }

  .about-grid { grid-template-columns: 1fr; gap: 40px; }

  /* Technology page */
  .problem-grid  { grid-template-columns: 1fr 1fr; }
  .platform-grid { grid-template-columns: 1fr; }
  .focus-grid    { grid-template-columns: 1fr 1fr; }
  .collab-grid   { grid-template-columns: 1fr; }
}


/* ===========================
   MOBILE — 640px
   =========================== */
@media (max-width: 640px) {
  /* Nav */
  .nav-links {
    display: none;
    flex-direction: column;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--white);
    border-bottom: 1px solid var(--hairline);
    padding: 16px;
    gap: 4px;
  }
  .nav-links.open { display: flex; }
  .hamburger { display: flex; }
  .nav-cta    { display: none; }  /* モバイルではハンバーガーメニューに集約 */

  /* Landing page */
  .hero { padding: 80px 20px 64px; }
  .hero-content { max-width: 100%; }
  section { padding: 64px 20px; }

  .tech-cards,
  .news-grid,
  .team-grid { grid-template-columns: 1fr; }

  .about-stat-grid { grid-template-columns: 1fr 1fr; }

  /* Technology page */
  .page-hero { padding: 60px 20px 48px; }
  .content-section { padding: 56px 20px; }

  .problem-grid,
  .focus-grid { grid-template-columns: 1fr 1fr; }

  .approach-item { grid-template-columns: 1fr; }
  .approach-num  { width: 44px; height: 44px; }

  /* Article/News pages */
  .article-hero { padding: 48px 20px 40px; }
  .article-body { padding: 40px 20px 60px; }

  .related-grid   { grid-template-columns: 1fr; }
  .collab-pillars { grid-template-columns: 1fr; }

  /* Footer */
  .footer-inner { flex-direction: column; align-items: flex-start; }
}