A circle made from 3 points you move yourself. Will find use in my next game, enjoy this technical project I guess. Drag the points. Press c or p to see debug
If you were wondering how I made this, I first found the determinants of the minors cooresponding to the coordinates of the points, then used some formulae to turn them to parametric equations the pen can use. If you get a straight line, you must have put the points on one line.