no no no, this is a space invaders game, let me explain, we (as in humans and the spaceship in this game) live on earth whereas all the other things (including the asteroids/rocks in the game) reside in space, so technically we are the ones invading space, hence the name Space Invaders.
a. hearts stand for his love of daisy which gets him killed
b. history books stands for his childhood and his past dealings
c. money sign stands for the conflict of old money vs. new money
d. he shoots money because whenever something bad is happening, he spends money such as buying a new car or taking someone out to an expensive restaurant
 "Space Invaders"){kind=icon}
 "The Great Gatsby"){kind=icon}
 "You vs. Zombies!"){kind=icon}