Should add a new meta-energy purchase - only spawn bubbles from the best current ball. As it stands, I only have one bouncing at a time when I'm actively playing, because getting bubbles from lesser balls holds you back a lot.
The mechanics of your run 'n' catch zombies are just annoying when your car gets upgraded. I know the game is quite illogical in and of itself, but I hate seeing those f*ckers catch up when I'm going like 100+ MPH.
There should be another achievement called "Leave No Stone Unturned", which would require the player to clear off ALL of the Standing Stones on level 18, AND to place the maximum amount of towers possible on the map.
We have "custom numbers format" on our to-do list. Your preference should be possible when we add it.