fix for #24

src/main/java/de/srsoftware/web4rail/tiles/TileWithShadow.java

@@ -0,0 +1,33 @@
+package de.srsoftware.web4rail.tiles;
+
+import java.util.Vector;
+
+import de.srsoftware.web4rail.BaseClass;
+
+public class TileWithShadow extends Tile {
+	private Vector<Id> shadows = new Vector<Id>();
+	
+	public void add(Shadow shadow) {
+		shadows.add(shadow.id());
+	}
+	
+	@Override
+	public boolean move(int dx, int dy) {
+		boolean moved = super.move(dx, dy);
+		if (moved) placeShadows();
+		return moved;
+	}
+
+	public void placeShadows() {
+		removeShadows();
+		for (int dx=1; dx<width(); dx++) plan.place(new Shadow(this, x+dx, y));
+		for (int dy=1; dy<height(); dy++) plan.place(new Shadow(this, x, y+dy));
+	}	
+	
+	protected void removeShadows() {
+		while (!shadows.isEmpty()) {
+			Tile tile = BaseClass.get(shadows.remove(0));
+			if (tile instanceof Shadow) tile.remove();
+		}
+	}
+}