Added straightforward hover behavior for all units. Give a unit a nonzero Altitude: in its Mobile: block and the WithShadow: trait to make it hover.

OpenRA.Mods.RA/Move/Mobile.cs

@@ -30,6 +30,7 @@ namespace OpenRA.Mods.RA.Move
 		public readonly int Speed = 1;
 		public readonly bool OnRails = false;
 		public readonly bool SharesCell = false;
+		public readonly int Altitude;
 
 		public virtual object Create(ActorInitializer init) { return new Mobile(init, this); }
 
@@ -110,7 +111,7 @@ namespace OpenRA.Mods.RA.Move
 		int2 __fromCell, __toCell;
 		public SubCell fromSubCell, toSubCell;
 
-		int __altitude;
+		//int __altitude;
 
 		[Sync]
 		public int Facing
@@ -120,11 +121,7 @@ namespace OpenRA.Mods.RA.Move
 		}
 
 		[Sync]
-		public int Altitude
-		{
-			get { return __altitude; }
-			set { __altitude = value; }
-		}
+		public int Altitude { get; set; }
 
 		public int ROT { get { return Info.ROT; } }
 		public int InitialFacing { get { return Info.InitialFacing; } }

OpenRA.Mods.RA/Move/Move.cs

@@ -95,6 +95,14 @@ namespace OpenRA.Mods.RA.Move
 		public override Activity Tick( Actor self )
 		{
 			var mobile = self.Trait<Mobile>();
+			var info = self.Info.Traits.Get<MobileInfo>();
+
+			if (mobile.Altitude != info.Altitude)
+			{
+				if (mobile.Altitude < info.Altitude)
+					++mobile.Altitude;
+				return this;
+			}
 
 			if (destination == mobile.toCell)
 				return NextActivity;

OpenRA.Mods.RA/Render/WithShadow.cs

@@ -13,6 +13,7 @@ using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Traits;
 using OpenRA.Mods.RA.Air;
+using OpenRA.Mods.RA.Move;
 
 namespace OpenRA.Mods.RA.Render
 {
@@ -25,7 +26,7 @@ namespace OpenRA.Mods.RA.Render
 			var move = self.Trait<IMove>();
 
 			/* rude hack */
-			var visualOffset = (move is Helicopter && move.Altitude > 0)
+			var visualOffset = ((move is Helicopter || move is Mobile) && move.Altitude > 0)
 				? Math.Abs((self.ActorID + Game.LocalTick) / 5 % 4 - 1) - 1 : 0;
 
 			var shadowSprites = r.Select(a => a.WithPalette("shadow"));