Hey there, MikoTriko!
Thank you for the feedback. We only built 2 power-ups and 10 levels worth of level-up choices, but it sounds like most people are getting to about level 15 when the countdown timer runs out. I think adding more power-ups to the pool would do a lot more than just adding more levels to the current ones. The current level-up system shuffles a list of available power-ups and presents the player with up to 4 choices. Since there are currently only 2 power-ups in the pool, every level-up presents the player with the same choice.