Demonstrative Speech----No idea!

HELP ME! I HAVE NO IDEA!

I want to do the demo about Rubik's cube but i am afraid the audiences will get bored easily as some might not like to solve cube. However, i am in Engineering class, they all are supposed to like complicated things, am i right?

Besides, i am thinking to do card tricks. However, i am also afraid that some might have known the tricks.

Please give me some suggestions!