That is not a version compatibility thing. The 3D viewport window was maximized. Press Ctrl+Down Arrow over the Blender window to return it to normal mode.
To make your animation work: You cannot use the armature modifier with the Game Engine. The only way I know of to make armatures work is to select the mesh object and then the armature together with it and press Ctrl+P to make the armature the parent of the object. Follow these steps to do this in you file:
- Select the tentacle mesh.
- Delete the armature modifier from the stack.
- Press Alt+P over the 3D viewport window and select “Clear parent and keep transformation (Clear Track)”.
- While the tentacle mesh is still selected, Shift+Right Click the armature to select it as well. It is very important for the armature to be the active object, that is, the last object selected when multiple objects have been selected.
- Press Ctrl+P and select “Armature”, then “Don’t create groups” (you already have your vertex groups created, so don’t let Blender try to do it again or they will get messed up).
If you have followed these steps, your tentacle will now work in the Game Engine. A couple of extra notes:
- If you look in the tentacle’s modifier stack you will now see an entry called “Armature parent deform”. It has no options but a “Make Real” button. Don’t click the “Make Real” button or the armature will stop working in the Game Engine.
- You may already be aware of this, but SubSurf does not work in the Game Engine. You will need to apply your SubSurf modifier to see the extra geometry in your game.