diff --git a/app/src/main/java/net/imshit/aircraftwar/element/AbstractFlyingObject.kt b/app/src/main/java/net/imshit/aircraftwar/element/AbstractFlyingObject.kt
index def266d..b60b744 100644
--- a/app/src/main/java/net/imshit/aircraftwar/element/AbstractFlyingObject.kt
+++ b/app/src/main/java/net/imshit/aircraftwar/element/AbstractFlyingObject.kt
@@ -8,7 +8,7 @@ abstract class AbstractFlyingObject(
     val game: Games,
     initialX: Float,
     initialY: Float,
-    protected val speedX: Float,
+    protected var speedX: Float,
     protected val speedY: Float
 ) {
     var x: Float = initialX
diff --git a/app/src/main/java/net/imshit/aircraftwar/element/aircraft/enemy/Enemies.kt b/app/src/main/java/net/imshit/aircraftwar/element/aircraft/enemy/Enemies.kt
index cd61e25..7146b7c 100644
--- a/app/src/main/java/net/imshit/aircraftwar/element/aircraft/enemy/Enemies.kt
+++ b/app/src/main/java/net/imshit/aircraftwar/element/aircraft/enemy/Enemies.kt
@@ -27,9 +27,9 @@ sealed class Enemies(
     shootStrategyFactory = EnemyShootStrategyFactory(game),
     shootNum = shootNum
 ), EnemyListener {
-    val credits: Int = 0
+    open val credits: Int = 0
 
-    fun prop(): List<Props> {
+    open fun prop(): List<Props> {
         return listOf()
     }
 
diff --git a/app/src/main/java/net/imshit/aircraftwar/element/prop/factory/PropFactories.kt b/app/src/main/java/net/imshit/aircraftwar/element/prop/factory/PropFactories.kt
index d5ff3fc..3e568ff 100644
--- a/app/src/main/java/net/imshit/aircraftwar/element/prop/factory/PropFactories.kt
+++ b/app/src/main/java/net/imshit/aircraftwar/element/prop/factory/PropFactories.kt
@@ -3,9 +3,9 @@ package net.imshit.aircraftwar.element.prop.factory
 import net.imshit.aircraftwar.element.prop.Props
 import net.imshit.aircraftwar.logic.Games
 
-sealed class PropFactories(val game: Games) {
+abstract class PropFactories(val game: Games) {
     val speedX = 0f
     val speedY = 0.1f
 
-    abstract fun createProp(x: Float, y: Float): Props
+    abstract fun createProp(x: Float, y: Float): Props?
 }
\ No newline at end of file