Oh i get it!
Actually you can only walk 1/4th a tile at the time, not a totally free movement, because the system let you turn/change direction even if you're 1/4th tile away from the center, give you the illusion of freedom, but still very controlled for easy moves.
I know what you feel about hardcore level from level 1 to end dude!
May i ask, did you beat the 16 level?