As an idea for improvements maybe implement a hiscore for each level saying the number of moves it took? I know this is a common idea used in puzzle games but I think it adds a hiscore that people can really compete for.
After a few hours I achieved 513k in survival but score didn't register D: love the game though, and only advice I have ontop of other peoples is when you have just big blues on the screen use them to go around in circles and heal up. I found this very useful around 300k and 400k in survival. Good luck all :)
well my advice for the hard badge is tried some souls on last kill x enemies level in area 3, should be 70 enemies as it pays 25k+ souls, upgrade bloodlust aura, trancendence (isn't it spelt transcendence?), soul tempest and inverse aura to max in everything, then I spammed spacebar and a direction with the occasional e to heal, if BP is low then attack a little with mouse click and you should get max again quickly, I also used combo ledger relic as i constantly got very high combos. Hope this helps :)
For those in need of help for teh Hostile Arena Challenge, start the challenge and shoot 1 bullet getting 100% accuracy, then just die and you will get 10K score for 100% accuracy. Hope this helps.
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good tip. combo ledger also saves you from unfair combo breaks if paired with slaughter chain.