Time for action – multiple erections

We're going to erect four invisible walls around the play area to keep the heart reined in.

1. Navigate to GameObject | Create Other | Cube.

2. Rename the new Cube GameObject Wall Back.

3. Give the Cube these transform settings in the Inspector panel:

   Position X: -0.15 Y: 1.4 Z: 1.6

   Rotation: X: 0 Y: 90 Z: 0

   Scale: X: 0.15 Y: 12 Z: 6

4. Uncheck the Mesh Renderer checkbox in the Inspector panel to make the back wall invisible to the player.

   

5. Repeat these steps to create three more Cubes called Wall Front, Wall Left, and Wall Right. The best way to do this is to duplicate the Front Wall three times. Just right-click/alternate-click the Wall Front GameObject and choose "Duplicate" from the context menu. These are the settings I used to place the other walls, but feel free to tweak them to suit your taste:

   Wall Front

   Position X: -0.7 Y: 1.4 Z: -2.4

   Rotation X: 0 Y: 90 Z: 0

   Scale X: 0.15 Y: 12 Z: 6

   Wall Left...