Thank you so much for the feedback :) It is super helpful for the development of the final game!
There are a couple of points that I am already planning for the next build; one of those is to remove the stop button so people really focus more on the percentage values in the tooltip to think strategically (also working on designs for better tooltips).
The global symbols are symbols that can appear no matter what card you select; there is a button where you can check those, but people are not noticing it.
Overall, I think that the game will need a dedicated tutorial level to introduce the mechanics more slowly. And more game events are on my plans too! :)