Huh, level 75 is not so hard at all. I stacked the jellies in the top left corner (about 350) and then all in on the enemy base. After conquering the base it is a piece of cake.
1) Open the game.
2) Sell all 'life'.
3) Place something heavy on the space button.
4) Leave the game for 20 minutes.
5) Earn the badges and close the game.