Needs more testing.
I don't really understand how the gamer is expected to win this. Yes, challenges are fun, but triple shockers make it so you literally cannot avoid being shocked without simply ignoring enemy units. Often after shocked, one of the three will make its way to the bottom to re-shock you as soon as you're recovered, creating a cycle which gives you no time to actually prevent the enemies from stealing ALL of your money. Find a way for the player to counter the shockers please.