Killer game programming in java - three questions - Worm

[Fernando hiar]

I have three questions about the game Worm in the Killer game in java book´s, why I use the value 0.7 in the bearing NorhWest, NorhtEast, SouthEast and SouthWest Why Don´t used the value 0.5 because this value is a half of 1 who i will walk in the straight ???
Why the fixedOfss[] = { 2, -2, -4}; has the value -4 and the value 2 and -2 the Points "walks" in two position is more quickly than 1 or - 1 whos walk in 1 position???
Why I used the cells[headPosn].x - RADIUS - x, it is to get the head more halfhead who´s the error if I don´t click in the center of head of Worm???

thank you,

Fernando.