Challenges - Gas Cost Vs. Stars Earned
I have been playing the challenges since they started. In the beginning, it is easy to accumulate stars quickly as the gas cost is low. As the challenge progresses, collecting stars becomes a pain as the gas cost increases considerably. NG should seriously think of either increasing the number of stars earned on higher levels or keeping the gas cost static.
Playing the game since 2015, Level 75 and 200K plus stars
Part of SG Woot since 2016. We have played more than 300 challenges and earned 4 million plus stars