/* ═══════════════════════════════════════════════════
   layout.css — App shell & grid
═══════════════════════════════════════════════════ */

#app {
  display: grid;
  grid-template-rows: 60px 1fr;
  /* Added a 4px column in the middle for the drag bar */
  grid-template-columns: 1fr 4px clamp(400px, 40vw, 700px); 
  height: 100vh;
}

/* ── The Drag Handle ── */
#drag-resizer {
  grid-row: 2;
  grid-column: 2;
  cursor: col-resize;
  background: var(--rim);
  transition: background 0.2s;
  z-index: 100;
}
#drag-resizer:hover, #drag-resizer.dragging {
  background: var(--phosphor);
}

/* ── Topbar ── */
#topbar {
  grid-column: 1 / -1;
  display: flex;
  align-items: center;
  gap: 0;
  padding: 0 20px;
  background: var(--deep);
  border-bottom: 1px solid var(--rim);
  position: relative;
  /* TASK 4 FIX: raised from 50 → 200.
     The D3 SVG creates a GPU-composited layer on mobile browsers that can
     bleed above a z-index:50 topbar. 200 ensures the topbar and any nav
     elements that descend from it always sit above the graph. */
  z-index: 200;
}

.topbar-logo {
  font-family: var(--font-mono);
  font-size: 0.9rem;
  letter-spacing: 0.3em;
  color: var(--phosphor);
  text-shadow: 0 0 12px rgba(0,255,136,0.5);
  margin-right: 32px;
  flex-shrink: 0;
}
.topbar-logo span { color: var(--muted); }

.topbar-nav   { display: flex; gap: 2px; flex: 1; }
.topbar-right { display: flex; align-items: center; gap: 16px; margin-left: auto; }

/* ── Graph panel ── */
#graph-panel {
  grid-row: 2;
  grid-column: 1;
  position: relative;
  /* Explicit z-index establishes a predictable stacking context.
     Must stay below topbar (200) and drag-resizer (100). */
  z-index: 1;
  background: var(--void);
  overflow: hidden;
}
#graph-panel::before {
  content: '';
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(var(--faint) 1px, transparent 1px),
    linear-gradient(90deg, var(--faint) 1px, transparent 1px);
  background-size: 40px 40px;
  opacity: 0.3;
  pointer-events: none;
}

/* ── Right panel ── */
#right-panel {
  grid-row: 2;
  grid-column: 3;
  background: var(--deep);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

/* ═══════════════════════════════════════════════════
   MOBILE RESPONSIVENESS (Phones & Small Tablets)
═══════════════════════════════════════════════════ */
@media (max-width: 768px) {
  #drag-resizer {
    display: none;
  }

  #app {
    grid-template-columns: 1fr;
    grid-template-rows: 60px 35vh 1fr;
  }

  /* Graph sits in row 2, below topbar */
  #graph-panel {
    grid-row: 2;
    grid-column: 1;
    z-index: 1; /* below topbar (200) — graph never bleeds over nav */
  }

  /* Chat panel sits in row 3, below graph */
  #right-panel {
    grid-row: 3;
    grid-column: 1;
    border-top: 2px solid var(--phosphor);
    z-index: 2; /* above graph so it can grow upward without clipping */
  }

  /* ── Mobile nav drawer ───────────────────────────────────────────────────
     If your HTML has a slide-in nav menu, add class="mobile-nav-drawer".
     z-index 300 puts it above topbar (200) so it overlays everything.

     Example:  <nav class="mobile-nav-drawer" id="mobile-menu">...</nav>
  ── */
  .mobile-nav-drawer {
    position: fixed;
    top: 60px;      /* flush below topbar height */
    left: 0;
    right: 0;
    z-index: 300;   /* topbar=200, graph=1 → drawer sits above both */
  }
}