Thanks for checking it out!
In playtesting, I did feel like it took a little too long to gather the souls for the final upgrades, since you're not always guaranteed to have them spawn...
I can tweak the numbers to lower it a bit more
The top branch of the tree focuses on increasing time, both base time, and giving a chance to grant some time on kills. Did you happen to grab any of those? Just curious as to what a regular player would prioritize over me as a developer
Regardless, thank you for taking the time to play and leaving some feedback!