[cbk1994]

Just use radians for your angle. Degrees is seldom used in programming.

PHP Code:

a = pi * 2 / 2; // 180 degree angle
// Of course, in this case, you can just use pi 


To turn 4 directions:

PHP Code:

a += pi / 2; 


To turn 8 directions:

PHP Code:

a += pi / 4;