/* ======================================================================
   OPERATING SYSTEMS PAGE – SUBJECT LEVEL STYLES
   This file EXTENDS main-page.css
   ====================================================================== */

/* --------------------------------------------------
   PAGE HEADING (Operating Systems Hub)
   -------------------------------------------------- */

.page-heading {
  padding: 4.5rem 1rem 3rem;
  text-align: center;
}

.page-heading h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  letter-spacing: -0.02em;
}

.page-heading .subtitle {
  margin-top: 0.75rem;
  font-size: 1.05rem;
  color: var(--text-secondary);
  max-width: 720px;
  margin-inline: auto;
}

/* --------------------------------------------------
   STABLE PLACEHOLDER GRID (NO FLICKER)
   -------------------------------------------------- */

.learning-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 1.75rem;
  margin-top: 2rem;
}

/* Placeholder state (Updated to span full width) */
.learning-grid:empty::before {
  content: "Engineering articles coming soon…";
  grid-column: 1 / -1; /* Added to center the message across the grid */
  display: block;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.95rem;
  padding: 4rem 1rem;
  border: 1px dashed var(--border-soft);
  border-radius: 12px;
  background: rgba(255, 255, 255, 0.02);
}

/* Added: Category Tag for future articles */
.os-tag {
  display: inline-block;
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--accent-blue);
  background: rgba(0, 122, 255, 0.1);
  padding: 0.2rem 0.6rem;
  border-radius: 4px;
  margin-bottom: 0.5rem;
  width: fit-content;
}
/* --------------------------------------------------
   HUB ARTICLE CARDS
   -------------------------------------------------- */

.os-article-card {
  text-decoration: none;
  color: inherit;
  background: var(--bg-secondary);
  border: 1px solid var(--border-soft);
  border-radius: 14px;
  padding: 1.5rem;
  transition: var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}

.os-article-card:hover {
  border-color: var(--accent-blue);
  box-shadow: var(--glow-blue);
  transform: translateY(-4px);
}

/* --------------------------------------------------
   NEW ARTICLE PAGE UPDATES (Process Management)
   -------------------------------------------------- */

/* 1. Pure White Header Text & Increased Size */
.breadcrumb-link {
    font-size: 1.4rem; /* Increased as requested */
    font-weight: 700;
    color: #ffffff !important; /* Pure white */
    text-decoration: none;
    margin-right: 25px; /* Distance between word and toggle */
}

/* Header Layout Adjustments */
.header-left {
    display: flex;
    align-items: center;
    gap: 15px;
}

.header-divider {
    width: 1px;
    height: 24px;
    background: rgba(255, 255, 255, 0.2);
}

/* 2. Full Width Content - Removing Card Look */
.full-width-content {
    width: 100%;
    margin: 0;
    padding: 0; /* Removes gap between header and title */
}

.article-body {
    max-width: 100%;
    padding: 1.5rem 5% 4rem; /* Tight top padding pulls title up */
    background: transparent;
    box-shadow: none;
}

.article-text {
    line-height: 1.8;
    font-size: 1.15rem;
}

/* 3. Toggle Button Styling */
.nav-toggle-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    padding: 0;
}

/* 4. Theme Background Color Logic */
body.article-light-mode {
    background-color: #ffffff !important;
    color: #000000 !important;
}

body.article-dark-mode {
    background-color: #0e1629 !important; /* Website standard blue */
    color: #ffffff !important;
}

/* Toggle Logic for Headings */
.article-light-mode h1, .article-light-mode h2 { color: #000; }
.article-dark-mode h1, .article-dark-mode h2 { color: #fff; }

/* 5. Footer Update */
.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 2rem 5%;
    border-top: 1px solid rgba(255,255,255,0.1);
}

.footer-links a {
    margin-left: 15px;
    text-decoration: none;
    color: inherit;
    font-size: 0.9rem;
}

/* --------------------------------------------------
   MOBILE OPTIMIZATION
   -------------------------------------------------- */

@media (max-width: 768px) {
  .page-heading {
    padding: 3.5rem 1rem 2.5rem;
  }

  .breadcrumb-link {
    font-size: 1.1rem; /* Slightly smaller for mobile screens */
  }

  .article-body {
    padding: 1rem 1.5rem 3rem;
  }
}