-float circleIn(float fraction, float start, float delta);
-float circleOut(float fraction, float start, float delta);
-float circleInOut(float fraction, float start, float delta);
+float circleIn(float fraction, float start, float delta, float slope);
+float circleOut(float fraction, float start, float delta, float slope);
+float circleInOut(float fraction, float start, float delta, float slope);