Use interfaces wherever it's possible in :api and :engine

api/src/main/java/com/bartlomiejpluta/base/api/game/entity/Entity.java

@@ -6,6 +6,8 @@ import com.bartlomiejpluta.base.api.internal.render.Renderable;
 import org.joml.Vector2i;
 
 public interface Entity extends Placeable, Renderable, Updatable {
+   void setStepSize(float x, float y);
+
    Vector2i getCoordinates();
 
    void setCoordinates(Vector2i coordinates);

api/src/main/java/com/bartlomiejpluta/base/api/game/image/Image.java

@@ -13,4 +13,8 @@ public interface Image extends Placeable, Renderable {
    int getWidth();
 
    int getHeight();
+
+   void setOpacity(float opacity);
+
+   float getOpacity();
 }

engine/src/main/java/com/bartlomiejpluta/base/engine/world/entity/manager/DefaultEntityManager.java

@@ -1,5 +1,6 @@
 package com.bartlomiejpluta.base.engine.world.entity.manager;
 
+import com.bartlomiejpluta.base.api.game.entity.Entity;
 import com.bartlomiejpluta.base.engine.core.gl.object.material.Material;
 import com.bartlomiejpluta.base.engine.core.gl.object.mesh.Mesh;
 import com.bartlomiejpluta.base.engine.util.mesh.MeshManager;
@@ -19,7 +20,7 @@ public class DefaultEntityManager implements EntityManager {
    private final EntitySpriteConfiguration configuration;
 
    @Override
-   public DefaultEntity createEntity(String entitySetUid) {
+   public Entity createEntity(String entitySetUid) {
       var material = entitySetManager.loadObject(entitySetUid);
       return new DefaultEntity(buildMesh(material), material, configuration);
    }

engine/src/main/java/com/bartlomiejpluta/base/engine/world/entity/manager/EntityManager.java

@@ -1,8 +1,8 @@
 package com.bartlomiejpluta.base.engine.world.entity.manager;
 
+import com.bartlomiejpluta.base.api.game.entity.Entity;
 import com.bartlomiejpluta.base.api.internal.gc.Cleanable;
-import com.bartlomiejpluta.base.engine.world.entity.model.DefaultEntity;
 
 public interface EntityManager extends Cleanable {
-   DefaultEntity createEntity(String entitySetUid);
+   Entity createEntity(String entitySetUid);
 }

engine/src/main/java/com/bartlomiejpluta/base/engine/world/image/model/DefaultImage.java

@@ -5,6 +5,7 @@ import com.bartlomiejpluta.base.engine.core.gl.object.material.Material;
 import com.bartlomiejpluta.base.engine.core.gl.object.mesh.Mesh;
 import com.bartlomiejpluta.base.engine.world.object.Sprite;
 import lombok.Getter;
+import lombok.NonNull;
 
 @Getter
 public class DefaultImage extends Sprite implements Image {
@@ -14,7 +15,7 @@ public class DefaultImage extends Sprite implements Image {
    private final int width;
    private final int height;
 
-   public DefaultImage(Mesh mesh, Material texture, int primaryWidth, int primaryHeight, int factor) {
+   public DefaultImage(@NonNull Mesh mesh, @NonNull Material texture, int primaryWidth, int primaryHeight, int factor) {
       super(mesh, texture);
       this.primaryWidth = primaryWidth;
       this.primaryHeight = primaryHeight;
@@ -23,4 +24,14 @@ public class DefaultImage extends Sprite implements Image {
       this.width = primaryWidth * factor;
       this.height = primaryHeight * factor;
    }
+
+   @Override
+   public void setOpacity(float opacity) {
+      material.setAlpha(opacity);
+   }
+
+   @Override
+   public float getOpacity() {
+      return material.getColor().w;
+   }
 }

engine/src/main/java/com/bartlomiejpluta/base/engine/world/map/layer/image/DefaultImageLayer.java

@@ -7,7 +7,6 @@ import com.bartlomiejpluta.base.api.game.map.layer.image.ImageLayerMode;
 import com.bartlomiejpluta.base.api.game.map.model.GameMap;
 import com.bartlomiejpluta.base.api.game.window.Window;
 import com.bartlomiejpluta.base.api.internal.render.ShaderManager;
-import com.bartlomiejpluta.base.engine.world.image.model.DefaultImage;
 import lombok.Getter;
 import lombok.NonNull;
 import lombok.Setter;
@@ -18,7 +17,7 @@ public class DefaultImageLayer implements ImageLayer {
 
    @NonNull
    @Getter
-   private DefaultImage image;
+   private Image image;
    private float imagePrimaryWidth;
    private float imagePrimaryHeight;
 
@@ -66,13 +65,13 @@ public class DefaultImageLayer implements ImageLayer {
 
    @Override
    public void setImage(Image image) {
-      this.image = (DefaultImage) image;
+      this.image = image;
       this.imagePrimaryWidth = image.getPrimaryWidth();
       this.imagePrimaryHeight = image.getPrimaryHeight();
 
       this.image.setPosition(x, y);
 
-      this.image.getMaterial().setAlpha(opacity);
+      this.image.setOpacity(opacity);
 
       recalculate();
    }
@@ -81,7 +80,7 @@ public class DefaultImageLayer implements ImageLayer {
    public void setOpacity(float opacity) {
       this.opacity = opacity;
 
-      this.image.getMaterial().setAlpha(opacity);
+      this.image.setOpacity(opacity);
    }
 
    @Override

engine/src/main/java/com/bartlomiejpluta/base/engine/world/map/layer/object/DefaultObjectLayer.java

@@ -8,7 +8,6 @@ import com.bartlomiejpluta.base.api.game.map.layer.object.ObjectLayer;
 import com.bartlomiejpluta.base.api.game.map.layer.object.PassageAbility;
 import com.bartlomiejpluta.base.api.game.window.Window;
 import com.bartlomiejpluta.base.api.internal.render.ShaderManager;
-import com.bartlomiejpluta.base.engine.world.entity.model.DefaultEntity;
 import lombok.Getter;
 import lombok.NonNull;
 import org.joml.Vector2f;
@@ -37,7 +36,7 @@ public class DefaultObjectLayer implements ObjectLayer {
 
    @Override
    public void addEntity(Entity entity) {
-      ((DefaultEntity) entity).setStepSize(stepSize.x, stepSize.y);
+      entity.setStepSize(stepSize.x, stepSize.y);
       entities.add(entity);
    }