Game mechanic update

Finally new mechanic is added to this game.

There are now 3 types of walls:

1. Normal walls (black): any sensor will activate
2. Only left walls (red): only left sensor will activate
3. Only right walls (blue): only right sensor will activate

Future sensors, walls and objects:

1. stop sensor
2. switch
3. ball and ball sensor

Note: New mechanic can be tested in level 2