I would like to submit a challenge that was given to me decades ago when the drafting board was still in use and the solution was obtained using descriptive geometry.
Four spheres of differing diameters must all contact each other at at four points of exact tangency. The actual diameters were not really important as long as they touch and they're all different. I've given specific diameters as it allows me to give you a check dimension to verify your solution. Given the four diameters and the three smaller sphere centers being coplaner as shown in the upper view, the rounded check dimension to the largest sphere would be 1.39600
The only dimensions you may input manually are the diameters of the spheres. Which means centerpoint locations, angles, tangent points etc may not be calculated and then manually entered as a constraint. All workplanes, sketches and features must be the result of geometric construction.
I was able to do it with 5 features. The challenge is not just the minimum number of features but to actually complete the model successfully.