float angle = 0;
int speed = 10;
int k = 0;

void setup()
{
frameRate(30);
size(500,500);  
background(120,120,120);
}
void draw()
{

background(120,120,120);
translate(width/2, height/2);
angle++;
rotate(radians(angle));
k = k + speed;
textSize(25);
text("rotate",-25-k,50+k);

if (k == 160) k=0;

}