I haven’t been on your site for a while. Sounds like you’re doing a great job. I hope it’s possible for us to meet up one day (you’re more than welcome to come and visit us here at UBC in Vancouver, BC).

I took a quick look at your site just now and I thought you’d be interested in some research which backs up the one-man scramble game you’re using to practice effectively. People do indeed prefer to get reinforced for good trials (rather than feedback on bad), when given the choice. Importantly, the positive reinforcement that comes from performing good trials (easier skills) seems to be important for long term learning and motivation. Of course, to improve, practising harder /challenging skills is necessary, but feeling good about how you are doing actually helps you retain things better.

So, in short, practice should involve a mixture of easier, rewarding skills/challenges as well as harder, difficult skills, in order to improve and maximize learning.

a few relevant references:
Chiviacowsky, S., & Wulf, G. (2007). Feedback after good trials enhances learning. Research Quarterly for Exercise and Sport, 78(2), 40-47.
Lewthwaite, R., & Wulf, G. (2012). Motor learning through a motivational lens. In NJ Hodges & AM Williams (Eds). Skill Acquisition in Sport: Research, Theory and Practice, 2nd edition (ch 10, pp173-). Routledge publishers.

Best,
Nicola