some minor edit in tiles

src/mightypork/rogue/world/EntityModel.java

@@ -46,7 +46,8 @@ public abstract class EntityModel<D, R extends RectBound> {
 	
 	
 	/**
-	 * Create a data object and populate it with default values.
+	 * Create a data object and populate it with default values.<br>
+	 * It's allowed to return null for no data.
 	 * 
 	 * @return data object
 	 */

src/mightypork/rogue/world/tile/Tile.java

@@ -14,6 +14,9 @@ public final class Tile extends Entity<TileData, TileModel, TileRenderContext> {
 	
 	public static final short ION_MARK = 700;
 	
+	/** Whether the tile is occupied by an entity */
+	private transient boolean occupied;
+	
 	
 	public Tile() {
 		super();
@@ -87,4 +90,29 @@ public final class Tile extends Entity<TileData, TileModel, TileRenderContext> {
 	{
 		return model.isWalkable(data);
 	}
+	
+	
+	public boolean hasItem()
+	{
+		return !data.items.isEmpty();
+	}
+	
+	
+	public Item removeItem()
+	{
+		if(!hasItem()) return null;
+		return data.items.pop();
+	}
+	
+	
+	public boolean isOccupied()
+	{
+		return occupied;
+	}
+	
+	
+	public void setOccupied(boolean occupied)
+	{
+		this.occupied = occupied;
+	}
 }

src/mightypork/rogue/world/tile/TileData.java

@@ -16,7 +16,4 @@ public abstract class TileData {
 	/** Items dropped onto this tile */
 	public final Stack<Item> items = new Stack<>();
 	
-	/** Whether the tile is occupied by an entity */
-	public boolean occupied;
-	
 }

src/mightypork/rogue/world/tile/TileModel.java

@@ -12,6 +12,12 @@ public abstract class TileModel extends EntityModel<TileData, TileRenderContext>
 		Tiles.register(id, this);
 	}
 	
+	@Override
+	public TileData createData()
+	{
+		return null;
+	}
+	
 	
 	/**
 	 * Test if this tile type is potentially walkable. Used during world

src/mightypork/util/math/color/Color.java

@@ -1,6 +1,7 @@
 package mightypork.util.math.color;
 
 
+import java.util.EmptyStackException;
 import java.util.Stack;
 
 import mightypork.util.annotations.FactoryMethod;
@@ -216,7 +217,7 @@ public abstract class Color {
 	 * Remove a pushed alpha multiplier from the stack. If there's no remaining
 	 * multiplier on the stack, an exception is raised.
 	 * 
-	 * @throws IllegalStateException if the stack is empty
+	 * @throws EmptyStackException if the stack is empty
 	 */
 	public static void popAlpha()
 	{
@@ -225,7 +226,7 @@ public abstract class Color {
 		}
 		
 		if (alphaStack.isEmpty()) {
-			throw new IllegalStateException("Global alpha stack underflow.");
+			throw new EmptyStackException();
 		}
 		
 		alphaStack.pop();