Introduce background spawning with parallax effect (#86)

Co-authored-by: Michal Pikulski <michal.a.pikulski@gmail.com>
Reviewed-on: #86

Assets/Scripts/Minigames/Airplane/Data/ParallaxLayer.cs

@@ -0,0 +1,24 @@
+namespace Minigames.Airplane.Data
+{
+    /// <summary>
+    /// Defines parallax layer depth for background elements.
+    /// </summary>
+    public enum ParallaxLayer
+    {
+        /// <summary>
+        /// Furthest back layer, moves slowest (lowest parallax factor).
+        /// </summary>
+        Background,
+        
+        /// <summary>
+        /// Middle layer, moves at medium speed.
+        /// </summary>
+        Middle,
+        
+        /// <summary>
+        /// Closest layer, moves fastest (highest parallax factor).
+        /// </summary>
+        Foreground
+    }
+}
+