/* PAGE HEADER */
.page-header-grid {
  position: absolute; inset: 0;
  background-image: linear-gradient(rgba(124,58,237,0.04) 1px, transparent 1px), linear-gradient(90deg, rgba(124,58,237,0.04) 1px, transparent 1px);
  background-size: 60px 60px;
  mask-image: radial-gradient(ellipse 100% 100% at 0% 50%, black 30%, transparent 100%);
}
.page-tag { color: var(--accent2); }
.page-tag::before { background: var(--accent2); }

/* FILTER */
.filter-btn:hover, .filter-btn.active { border-color: var(--accent2); color: var(--accent2); background: rgba(124,58,237,0.05); }

/* COURSES GRID */
.courses-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 1.5rem;
}

.course-card {
  background: var(--bg3); border: 1px solid var(--border);
  overflow: hidden; transition: all 0.3s; display: flex; flex-direction: column;
  cursor: pointer;
}
.course-card:hover {
  border-color: rgba(124,58,237,0.4); transform: translateY(-4px);
  box-shadow: 0 20px 40px rgba(0,0,0,0.4), 0 0 0 1px rgba(124,58,237,0.08);
}

.course-card-header {
  padding: 1.6rem 1.6rem 0;
  display: flex; align-items: flex-start; justify-content: space-between; gap: 1rem;
}
.course-num {
  font-family: var(--mono); font-size: 0.65rem; color: var(--muted);
  border: 1px solid var(--border); padding: 0.2rem 0.55rem; flex-shrink: 0;
}
.course-category-tag {
  font-family: var(--mono); font-size: 0.65rem; letter-spacing: 0.1em; text-transform: uppercase;
  padding: 0.2rem 0.6rem; border: 1px solid; flex-shrink: 0;
}
.tag-security { color: rgba(255,100,100,0.85); border-color: rgba(255,100,100,0.3); }
.tag-network  { color: rgba(0,229,255,0.85);  border-color: rgba(0,229,255,0.3); }
.tag-data     { color: rgba(124,58,237,0.9);  border-color: rgba(124,58,237,0.35); }
.tag-web      { color: rgba(80,220,120,0.85); border-color: rgba(80,220,120,0.3); }
.tag-os       { color: rgba(255,165,50,0.85); border-color: rgba(255,165,50,0.3); }
.tag-iot      { color: rgba(255,200,50,0.85); border-color: rgba(255,200,50,0.3); }

.course-card-body { padding: 1rem 1.6rem 0; flex: 1; }
.course-title { font-size: 1.1rem; font-weight: 700; line-height: 1.3; margin-bottom: 0.7rem; transition: color 0.2s; }
.course-card:hover .course-title { color: var(--accent2); }
.course-desc { font-size: 0.85rem; color: var(--muted); line-height: 1.6; }

.course-card-footer {
  padding: 1.2rem 1.6rem;
  margin-top: 1.2rem; border-top: 1px solid var(--border);
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
}
.slides-link {
  font-family: var(--mono); font-size: 0.72rem; color: var(--accent);
  text-decoration: none; letter-spacing: 0.05em; transition: all 0.2s;
  display: flex; align-items: center; gap: 0.4rem;
}
.slides-link:hover { gap: 0.7rem; }
.course-lessons { font-family: var(--mono); font-size: 0.68rem; color: var(--muted); }

/* RESPONSIVE */
@media (max-width: 768px) {
  .courses-grid { grid-template-columns: 1fr; }
  .course-card:hover { transform: none; }
  .course-card-header { padding: 1.2rem 1.2rem 0; }
  .course-card-body { padding: 0.8rem 1.2rem 0; }
  .course-card-footer { padding: 1rem 1.2rem; }
}

@media (max-width: 480px) {
  .course-title { font-size: 1rem; }
  .course-desc { font-size: 0.82rem; }
}