I was thinking the other day about how disappointing the Xmas event was this year. The one day SR was a washout when you have to pay to finish.
I think a better method as a one off would be to give you a exactly the right amount of energy to finish Sr. If you fail a level then you have to buy a can - no natural energy refills.
This would reward players for playing but add a new dimension and tension to every level as well as rewarding players who want to finish. Weaker players can replay the lower levels but still maybe get 2 completion milestones.
What do we think?