Tint not-yet-buildable asteroid area

src/ui/GameWorldView.cpp

@@ -918,15 +918,25 @@ void GameWorldView::drawTiles(QPainter& painter)
     const int rightTile  = leftTile + static_cast<int>(std::ceil(viewportWidthTiles())) + 2;
     const int bottomTile = m_config->world.heightTiles;
 
+    // Asteroid columns left of the buildable edge are not yet unlocked by
+    // expansion; tint them so the player sees the reachable-but-locked area.
+    const int buildableLeftX = -m_sim->currentAsteroidWidth_tiles();
+
     painter.setPen(Qt::NoPen);
     for (int x = leftTile; x <= rightTile; ++x)
     {
         const QColor& fill = (x < 0)
             ? m_visuals->asteroid.fill
             : m_visuals->space.fill;
+        const bool locked = (x < buildableLeftX);
         for (int y = 0; y < bottomTile; ++y)
         {
-            painter.fillRect(tileRect(QPoint(x, y)), fill);
+            const QRectF rect = tileRect(QPoint(x, y));
+            painter.fillRect(rect, fill);
+            if (locked)
+            {
+                painter.fillRect(rect, m_visuals->overlays.lockedAsteroid);
+            }
         }
     }
 }