As i know...
for left
x += Math.cos((rotation + 90)*Math.PI/-180)*speed;
y += Math.sin((rotation + 90)*Math.PI/-180)*speed;
for right
x += Math.cos((rotation - 90)*Math.PI/-180)*speed;
y += Math.sin((rotation - 90)*Math.PI/-180)*speed;
for back
x += Math.cos((rotation + 180)*Math.PI/-180)*speed;
y += Math.sin((rotation + 180)*Math.PI/-180)*speed;
for forward
x += Math.cos((rotation)*Math.PI/-180)*speed;
y += Math.sin((rotation)*Math.PI/-180)*speed;