The Crowtail- Logic Block allows you to play with logic gates by literally plugging one into another and watching the progression of an input to an output!
Each Logic Block represents a different logic function: the NOT block is a simple inverter, where the output is the opposite of the input. The AND block will only output a 1 if both of the inputs are 1. The OR block will output a 1 if either of the inputs are 1. There are also input blocks and splitter blocks.