Thanks! Sorry for the late reply. Actually, what you are asking is king of a similar question to one of the questions I was asked in the interview mentioned above. I quote:
"Small Dev Talk: Are there any player progression or upgradable features in Quick Slick Deadly?
Siavash Tazari: As far as progression is concerned, the player starts playing as the fighter first and will unlock the survivor after playing five tutorial missions. In the same manner, the trickster can be unlocked by playing five tutorial missions with the survivor. I wanted the player to get to know each of these classes in exactly this order, because otherwise, the process of learning the game could have become quite confusing. Then, as mentioned before, there is a reward to unlock by finishing all missions with all three classes. Upgrades in the sense of permanent benefits as you progress through the game are not available. But within each mission, you have the possibility to increase the level of your boost ability to be able to go at faster speeds, and also the level of your power, which has different effects on different classes. The fighter benefits from a higher area of effect for its primary weapon when reaching each next power level, while for the trickster, the active time for using its boomerang increases, which could both be good and bad, but then again, combining great power with great risk makes up the entire philosophy behind the trickster’s gameplay. Playing as the trickster is by far the most challenging."