Aww... The moment you finish the story it gives you such a deep sense you have accomplished a long journey. I feel I miss some of the characters... the drunk squirrel :'D
Thank you for this little bit of color in this grey world
So damn much fun.
Here some tips:
Most of the score you have to do it on the first part. Try to take advantage from dangerous and 'stack' bonus as much as you can.
Don't 'edge' abuse or you won't be able to get a good bonus when the king will fly.
Done it after few tries with a multiplier of 20x and nearly 60k on stacking cake; still 88k points
For those after impossible badge remember that cheats are ALLOWED. You can try to balance cheats and handicaps so you can still have useful perks like shield dropped by foes (that massively increase your chance to survival during levels) with a decent score multiplier.
I would like to share what I hope is a useful tip:
At the beginning of each level and between each wave you can hold your main weapon to increase its effectiveness (so it doesn't get wasted).
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 "GemCraft chapter 0"){kind=icon}
 "The Grey Rainbow"){kind=icon}
 "Star Claws"){kind=icon}
 "Solipskier"){kind=icon}
 "Aliens Kidnapped Betty"){kind=icon}
 "Save Toshi"){kind=icon}
 "Feed the King"){kind=icon}
 "Knightfall 2"){kind=icon}
 "Anika's Odyssey"){kind=icon}
 "Gamma Bros"){kind=tracking}
 "My Pet Protector 2"){kind=icon}
 "Raiders took my dog"){kind=icon}
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 "Bullet Heaven 2"){kind=icon}
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Yeah, clever use of cheats can make the game a bit easier!