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);
+            }
         }
     }
 }

src/ui/VisualsConfig.h

@@ -49,6 +49,7 @@ struct OverlayVisuals
     QColor tileHighlight;
     QColor selectedOutline;
     QColor copyConfig;
+    QColor lockedAsteroid;
 };
 
 struct ToastVisuals

src/ui/VisualsLoader.cpp

@@ -225,6 +225,7 @@ VisualsConfig VisualsLoader::load(const std::string& path)
         cfg.overlays.tileHighlight   = parseColor(requireString(ov, "tile_highlight",   "overlays"), "overlays.tile_highlight");
         cfg.overlays.selectedOutline = parseColor(requireString(ov, "selected_outline", "overlays"), "overlays.selected_outline");
         cfg.overlays.copyConfig      = parseColor(requireString(ov, "copy_config",      "overlays"), "overlays.copy_config");
+        cfg.overlays.lockedAsteroid  = parseColor(requireString(ov, "locked_asteroid",  "overlays"), "overlays.locked_asteroid");
     }
 
     // Toast