While visiting my favourite Arcade/Flipper-museum (http://for-amusement-only.de), my games had their first betatest, which was quite helpfull.
Especially Zerocron got a lot of small changes afterwards:
-no more shootable asteroids in the shoplevel (too confusing)
-the size of the levels now increases while progressing, which reduces the difficulty a bit and gives the turbo more sense
-the first level of all weapons is now free
-credits are worth more
-replaced the radar into a less original but more intuitive box, originally it was surrounding the player
-tweaked a lot of effects, added screenshake for smartbombs
-added a rebound-shot as bonusweapon
Thanks to Ariane Fugmann for betatesting!