You can get hit and still get a "perfect" rating, you just can't lose a life. Once you have all 5 hearts your goal shouldn't be to never get hit, but to only get hit 4 times. You can plan your movement more effectively this way.
Soulbound/combination charge items need to have a very low, but non-zero, chance of dropping from non-bosses. This would allow players to have some power creep and lets them see real progress over time.
Don't use the cheat if you want the hard badge. Your score shows up as Cheater and you don't get the badge. Just wasted a ton of time this way, and there is absolutely no warning that you won't get credit. Absolutely absurd.
A tip for critical training: turn on the sound and close your eyes. The two different sounds can be much easier to react (or not react) to than the different images.
@will2345676, you got the first two badges in July of 2013. You didn't get the hard badge until June of 2014. If it took you 11 months to get to the point where you are getting 2k coins, coin acquisition is too slow.
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 "Swords and Souls"){kind=icon}
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 "Burrito Bison Revenge"){kind=icon}
 "Survival Lab"){kind=icon}
 "ELEPHANT RAVE"){kind=icon}
 "Kana Warrior / かなウォリアー"){kind=icon}
 "Mighty Knight"){kind=icon}
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 "Hippolyta"){kind=icon}
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Today I've introduced a research achievement which gives a bonus to the research output. I hope this helps a little.