The game doesn't reward you for completing the Human Mode, it punishes you with a mode that takes all the fun of the previous mode out of the game. The unlockable content should be an enjoyable challenge, this it is not.
My Hard Badge Tip: 1 point in Boost on Day 2. By Day 3 you should have enough for 1 off max in Boost and 2 off max in Ammo. Keep wheels level to ground and boost during the last hill holding left.
The game is kinda unclear at the end:
To beat the final boss first get to the far left lane and build up nitro
When rubbing up against the space ship jump right.
Slow down but keep your nitro.
Repeat this process on the right hand side, then the middle.
Easy once you know what to do.
Had a glitch where after getting all skills on the mage, I could press 4 for the Single Fear but it would cast Mass Fear and it would not be affected by cooldown... Game become a game of send the mage in and let the monsters kill each other.
Easy way to beat the hardest battles:
Make a deck based on the "Parting Gift" card. Add as many peasants, fresh skeletons, and mud golems as you can to about 10 gold, 3 iron, and 3 crystal mines. 3 Parting gifts is enough to ensure you will have one, then repairs, portal growths, and siege engines can be added as filler.
Surrender until you get a good starting hand.