Walls are now transparent when they are see through
Added glass walls

Glass walls acts like steel walls but are see through, perhaps creating
some gameplay elements that can guide players to the goal without
players being blind all the way through.
Resdesigned first level
Redesigned 2nd and 3rd level

1st level is redesigned as an intro to the same colored wall mechanic.
2nd level is redesigned to introduce having multiple colors. 3rd level
is redesigned to introduce color switching.
All in all these should help introduce player to different mechanics in
a more streamlined way.